#help-10
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Strong Induction, the TA is gonna be picky if I pick another method
ahh ok ok
mmm.... wait
I don't know I'm not sure I think 25
;<
need help
please
i don't know
please help me
No, I don't know, only the exercise says to calculate, that's as far as I know.
oh yes yes
Strong induction applies more to recursive functions
This is example with strong Induction
ahh, yes I know but it doesn't work for me or maybe there is another solution please help
oh it's spectacular
I have trouble with this form of induction too 😓😓
but i need a your help please
I need help too 🤣
We in this together 😂
yess
So... how gonna get help 🤔
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Hi so im learning how to find the perticular solution to this equation, The lecture is saying that because G(x)=x^2, y has to be a polinomial of degree 2. Can anyone explain why that is?
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Ok so I'm confused as to what the answer for this problem is. My professor said it is zero, but I said DNE because it's breaking one of the limit laws.
@patent marten Has your question been resolved?
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i think u should it to different server and see whether someone may help
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low key confusing 9th grade math
im kinda bad sry just learned this todayu
nvm solved on my own lmao
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why must n be a positive integer?
'must' is the wrong word here
it's not saying it must be an integer and otherwise the equality doesn't hold
I'm not quite understanding what you mean
you used the word "must" but it's not saying "must".
under the right hypotheses you can extend that to n being a real number and still have the equality
this is my first time doing limits so sorry if i sound dumb here 🥲
but it's making it easier for you
(i assume the question is asking you to prove that)
There's cases where the equation might fail, if n is not an integer
lim[x -> 0] √[x] is undefined
But √[lim[x -> 0] x] = 0
The problem is the discontinuity of √x, at the limit point.
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hello, how would you go about part c in this question
Simplify 5 - r/10
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The part that you colored blue is the part that B-A and C-A shares, so given that B-A=C-A mean that the C-A-B region and B-A-C region are empty
Or else there will be elements that are in B or C that isn't in the blue part
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It would be helpful if someone can explain the concept behind this sort of problem as well it would be much appreciated
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how do you solve using hyperbolic functions? I tried integration by parts but i got stuck. u = tanh^-1(x), du = 1/1-x^2, dv = x and v = x^2/2. when i do the integral of v du, im not sure how to proceed
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now idk how to find for what values
it would be inconsistent
Ik this wont have any solutions because second last row concludes that 0 = 1
whenever you divide by something, make sure that the something isn't zero
oh so since 0 = a - 2b
I cant divide row 3 by it?
if a-2b=0, then you can't divide by it
so there are two cases
either it is zero or it isn't
shit im confused
so do I split it into two cases
before doing that
but ltte say
if a - 2b neq 0
then the rref would be the same as what I got right
and the rref I have is incosistent too right
$\forall \alpha, \beta \in \mathbb{R}$
adzetto
why
because this is present regardless of the values of α and β
I am a bit worried that the program gives that rref
it should absolutely depend on the values of alpha, beta
as mine
instead of alpha and beta plug in zero
what do you get then
(you should obviously get a consistent system because the last column is the zero column)
wait
so all 0s
on the right side?
there we go
online calc can't handle variables correctly
so for one case im alrdy done right
yes
alright imma do case 2 rq and show u brb
uhhh another question
I was thinking about dividing row 3 by a
but i will have to split it into cases again right so is there a better way
just do it
you have two variables so it's not a huge surprise that you have to split it into cases two times
again doe
so a = 0 and a neq 0
yes
shit alr brb
well now the third row is 0 0 0 0
and then say its inconsistent
and if a=0 and a-2b neq 0, then b has to be neq 0
ah
so a = 0 and a - 2b = 0
well then b has to be zero
ohhhhh wb
so fourth row is also 0 0 0 0
you are overcomplicating this
ah mb
but
im confused
how did u conclude
that b = 0
from thsi
oh because
a - 2b = 0
a=0 and a-2b=0
what
anything with a zero on the right is always consistent
to plug in b = 0
wait so ur sayinf
this matrix is consistent?
so the answer would be for all a, b in R s.t a and b neq 0?
yes and the negation of that is a neq 0 or b neq 0
yes
for all a, b in R s.t a neq 0 or b neq 0?
again, yes
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can anyone help me with how to prove a Cobb-Douglas function is homothetic
what's a homothetic function
a homothetic function can be written as $f\circ g$ where f is monotonic and g is homogeneous (ie $g(sx_1,...,sx_n) = s^kg(x_1,...,x_n)$)
yes, but now it's like I know u = $f\circ g$ but I dont know f and g , and I need to prove u is homothetic
CCCCClaire
yes, well you have to find f and g such that it works
here i should be 1
so can I say if (the partial derivative of tx1 / the the partial derivative of tx2 )= (the partial derivative of x1 / the the partial derivative of x2), then u is homothetic?
t is a constant
rafilou2003
uh lemme check
you should be able to write the utility function as $(x_1^{\frac{\alpha}{\alpha+\beta}}x_2^{\frac{\beta}{\alpha+\beta}})^{\alpha+\beta}$
rafilou2003
ooh right
what's k
some integer
and btw if I want to show u() is qusai-concave can I use its borded Hessian determinant ?
wth i've never heard of these words
or just use its second order derivative and say if it is concave, then it is quasi-concave
yeah concave => quasi-concave
I think that's the case here
thank u so much!
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Need help with this functional equation: f(x^2 + f(y)) = x•f(x) + y
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do you know some other sets that generate A_n?
This is all information that was given
this can't be the only thing you know about A_n
ill give the full question for clarity:
What is your definition of A_n?
It is not defined anywhere so i dont really know
surely your book defines the symbol A_n at some point
Im trying to look for it right now
okay i found it A_n is the set of all even permutations
And what is an even permutation
definiton from the book says: A permutation that can be written as an even number of transpositions
So do you see how the s_i s_j generate A_n
not sure
@storm kayak Has your question been resolved?
@storm kayak Has your question been resolved?
@storm kayak Has your question been resolved?
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@storm kayak Has your question been resolved?
Why did the bot just stop asking?
@wide star
It only asks for few times then it just stops
I think it keeps asking but the waiting interval increases exponentially, right?
im in hs ineed help with my algebra
using this, what set would generate A_n for sure
@storm kayak Has your question been resolved?
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Idk if you're still here, but #groups-rings-fields is probably a better place to ask future abstract algebra questions, more knowledgeable people will be there
Which part are you confused about though? Can you show that that set generates S_n?
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How would I prove that the directrix of the quadratic function of the form y = ax^2 is vertical?
@wanton carbon Has your question been resolved?
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also i want to show uniqueness
prove that there is no other directrix for this quadratic function
Let $P(x, ax^2)$ be an arbitrary point on the parabola $y = ax^2$. Let $F = (f_x, f_y)$ be the focus of the parabola $y = ax^2$, and let $d$ be the directrix by $y = c_1 x +c_2$. Use definition $$\mathcal{P} = { P \in \mathbb{R}^2 \mid d(P, F) = d(P, d) }.$$ Then find $f_x, f_y, c_1, c_2$ using the polynomial equation. This can be algebraically tiring. You can then use a reductio ad absurdum argument to prove uniqueness. Having found $F\left(0, \frac{1}{4a}\right)$ and $\left(c_1, c_2\right)=\left(0, \frac{-1}{4a}\right)$, using the same definition, assume $y=c$ and $c\neq \frac{-1}{4a}$ and show that there cannot be such a $c$.
adzetto
@wanton carbon Has your question been resolved?
One second though this is assuming we just have the equation of y = ax^2
this is part of a large proof
so we don’t know it’s a parabola yet
basically solved but one second
What
If you want a complete proof, do you want to define/demonstrate algebraic elements, real numbers and many more?
I think it would be quite redundant
ok fair enough
is there a way other than just the definition of a parabola to show that it can only have one focus
@shrewd wasp
Let $F_1 = (f_{1x}, f_{1y})$ $F_2 = (f_{2x}, f_{2y})$. Then again use the definition $d(P, F_i) = d(P, d_i)$. you'll have seen it $F_1 \equiv F_2$
adzetto
can u put this more plainly pls?
I’m an amateur
It should already have a single focus by definition, but if you want, assume that it has two foc such as F1 and F2. Write the equation for both focus using the definition. You will see that F1 and F2 must be the same point.
No problem, I'm studying engineering anyway.
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help is (4,38 )correct
!status
What step are you on?
1. I don't know where to begin
2. I have begun but got stuck midway
3. I got an answer but I'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
i jus need to verify my aswnser
(4)
^i didnt do the equation yet, since i want to check if i got the coords correct
aha, lets see
y=8x+4, m=-1/8
f'=-1/x^(3/2)=-1/8
x^3/2=8, x=4
original if you want the y coordinate
because when i plug into the orginal i get 32
oh okay tytyt
32 looks like a devious number, so i wasnt too sure
how do you get 32?
y=8(4)+4
thats 36, but also thats not the equation of the graph my guy
wait so what do i do
the graph has the equation f(x)=2/sqrt(x) +1
np
wait i dont wanna bother, but can you also explain this question
(you dont have to, but i was jus confued on it)
you can check the limits in either direction (+ or - infinity)
if f(x) is convergent to a value rather than infinity or - infinity then that can be considered an asymptote
im not sure how youd use that formula specifically for this honestly, ive only ever used it for differentiation
ill do some reading though and come back if i find anything
its okay i can give u a differnt problem ! (i was jus confused on how to factor out the x^2 for this one )
if you multiply the numerator and denominator by 1/x though then take limits to +inf and -inf it should come out cleanly though
i dont think you can factor out x^2 really, however, if you divide the numerator and denominator by x^3/2 and then take the limit it should be clearer
ah okay tyty
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Hello I am doing Statics homework which requires some Calc 3 vector math. I have unlimited attempts and I have been using them to check my answers. I am stuck on questions 4-9. I have my work but will include a picture of the question first.
** Note: It's just one question, but divided to 10 steps
Question:
Force F1 has a magnitude of 473N and force F2 has a magnitude of 514 N. h = 3.9 m,
1- Determine Force F1's x-component in N ? = 0
2- Determine Force F1's y-component in N ? = -216 N
3- Determine Force F1's z-component in N ? = -421 N
4- Determine Force F2's x-component in N ? = 210.7 N (incorrect)
5- Determine Force F2's y-component in N ? = 422 N (incorrect)
6- Determine Force F2's z-component in N ? =-206 N (incorrect)
7- Calculate the Resultant force's magnitude in N ? 693N (incorrect)
8- Calculate the resultant force's coordinate direction angle θx in Deg ? = 72 degrees (incorrect)
9- Determine the Resultant force's coordinate direction angle θy in Deg ? = 67 degrees (incorrect)
10- Determine the resultant force's coordinate direction angle θz in Deg ? = 155 degrees
so what i have done:
find the unit vector of F2 (direction vector of length 1)
multiply each component of the unit vector by the length of F2
obtaining F2's components using the unit vector
u2 is a unit vector, of length 1, in the direction of F2.
when i multiply the magnitude of F with u2 i get the components of F2.
look, if i take the magnitude of F2's components i get 514 N,
and when i take the magnitude of u2 i get 1.
i think my teacher might be wrong so i want to double check
Hmm
For F2 I got this
$\bar{F_2} = \left \langle250.832, 376.25, -244.664 \right \rangle \mathrm{N}$
okay, where do you think I might have gone wrong?
okay, accounting for z being -z direction, i used the components you found and it was correct
VulcanOne
Alright
i see what you are talking about, except my teachers notes confused me because of a problem similar to this where he did not do 8-2 = 6
I think from there you can redo your work and you'll hopefully get the correct answers
Yeah it can get confusing just writing one number
So I always write my ending coordinates and starting coordinates to tell myself where the vector was going and where it started
thats how i started but i was following this example and he was trying to show us some short cut but I dont think i can use it for this homework problem. look at this example we did in class and how easy it was to find the position vectors (r)
thank you very much btw VulcanOne
Just writing the results is pretty confusing to me. Not sure where the shortcut is.

Also the notation is a bit off
For the magnitude, you'd use this
true
$\norm{\overrightarrow{r_{AB}}}$
VulcanOne
yeah, the notation has been really messing with me. Since in Calc 3 we use one notation, and in Physics they used another one, and my engineering professor is just barely using any proper notation 😅 🥲

Wait are you structural engineering?
Electrical & Computer Eng.
Ooooo
got me like this🧟
Same lmao
its a very humbling experience
Hope we make it into the big leagues soon 
are u doing structural?
Yep. Civil engineering. But structural is like 80% of the entire career so yeah :)
That sounds awesome and also very humbling 😅
so i was wondering what points u used for the starting coordinates
I used the point where the forces where exiting
Point A
And the other 2 points I used as the end points
Since direction matters
And the forces have their arrows pointing that way so ye
if i use A (0,2,3.9) how is it when i get the vector AB, it is <0,-2,-3.9>? when the z point of A was positive?
i am just confused on where i need to do the book keeping
ooooh wait i see it now....i was counting point A as (0,0,0) idk why
i was trying to use free body diagram technique
Well it can get messy if you relocate your origin
so i just keep the origin at the original given one? no shortcuts?
okay
You won't lose track easily
And you can look at the diagram and it will be your reference
You're right and I think everything messed up when i found the magnitude of AC = <4, 8,.-3.9>, since it should be AC = <4, 6, -3.9>
that little difference ruined everything after that
i swear these little things are going to keep me from getting A's this semester
You'll get an A I'm sure 
Keep things as simple as possible
You'll get the A+ in the bag
Also time yourself and know where you are messing up and try to fix them
No shortcuts until you understand the process
After that you will shortcut automatically
thats some great advice that didn't know i needed...
I just finished the homework and got everything correct, thanks again bro
idk if ur accepting FR's but u should add me if you ever need another eye or helping hand!
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Is this correct?
You should write negative sign in step 2 instead of absolute value. $$\int_{-1}^1 -\frac{3}{4}x+\frac{3}{4} dx - \int_{1}^2 -\frac{3}{4}x+\frac{3}{4} dx$$
Since $$\int_{1}^2 -\frac{3}{4}x+\frac{3}{4}x dx$$ has a negative area.
Good
Hmm, the value I got is 9/8
From step 4 to step 5, you forgot your negative sign.
My teacher just suddenly started writing wrong equations and I got confused lol
Thanks!
Welcome.
Good
My bad, since I copy-pasted it.
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if f(x)=1+xlnx for (0,5], what is its minimum and maximum value within the domain
Min/max should ring you a bell about derivatives, right?
right, so the minimum i found to be 1/e by simply equation the derivative to 0
but for the maximum, im not tpoo sure
intuitively, i would say x=5 but without proper working out
ah
so how would i word this
as x increased, f'(x) increase, therefore the greatest x would yield the greatest f(x)
but this is kinda weird to write in a maths problem
it wants you to explain?
You always test the highest and lowest values in the domain
so 0, 5, and then the value in the domain where f'(x) = 0
well i cant test 0 since lnx
0 technically isn't in the domain, but as you approach 0 from the right you get 1
the limit approaches 1?
it does, but I guess that's not obvious without looking at the graph
but the derivative is negative between 0 and 1/e
so the minimum is def 1/e
so yea it's 5 because that's the one with the greatest value of the 3 significant values
yes
x^2+xy+y^2=1
what is the max and min y values possible?
i found the derivative to be -(2x+y)/(2y+x)=0
i think you can just rearrange for y explicitly
like, you can get y = f(x)
and then go normally
how would you do that
ok suppose you had 1 + y + y^2 = 1, how would you solve for y
quadratic
right
or just factorise
so just do that for x^2 + xy + y^2 = 1
i mean ok
you don't need the quadratic formula for this, it's actually nicer to use completing the square when you have algebra i find
maybe slightly simpler
but both work
ok wait i'm dumb
given this
for now let's just multiply through by the denominator
wait i meant y'=that
i mean ok but you want y' = 0
yeah
so yeah you have -(2x+y) = 0
and then you can just substitute that back into the original thing
and then it's just quadratic again
that's probably how you're intended to do it
oh
ah i see your problem maybe i think
so let's just do it
y = -2x and x^2 + xy + y^2 = 1
so x^2 - 2x^2 + 4x^2 = 1
so 3x^2 = 1
so x = +-1/sqrt(3) and then y = +-2/sqrt(3)
simple sign error
you probably had like y = 2x instead of y = -2x
oh yeah you're right
getting 3x^2 = 1
yup
x = ±1/sqrt(3)
ok so im having trouble on which to substitute, x=-1/2 y or y=-2x
either works
shouldn't matter should it?
solve for either x or y and then you can just use y = -2x to get the other one
but would x= something y be faster
no
yes
oh true
also since x^2+y^2+xy means the values of x and y can be interchanged, would y just be the same answer
right what is this called again?
y is maximum at x = -1/sqrt(3), and then y has max value 2/sqrt(3)
actually no scrap what i said
and then x is maximum at y = -1/sqrt(3) and x has max value 2/sqrt(3) there
oh wait nvm
so like, you can swap them in that respect
yeah thats what i meant, im confusing myself
actually
wait why is y max at -1/sqrt3 instead of the postive version
graph looks like this for reference
ok
so we have y' = 0 when x is either 1/sqrt(3) or -1/sqrt(3)
for x = 1/sqrt(3), y = -2/sqrt(3)
for x = -1/sqrt(3), y = 2/sqrt(3)
so one of these is a minimum and one is a maximum
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Suppose there are 2 real integers with a difference of 10. The smaller integer is a multiple of 3 whereas the other is a multiple of 7. If the sum of all the prime factors of each of the integers is 17, find the value of those 2 integers.
So.... the sum of the other prime factors would be 17 - 7 - 3 = 7
Which limits the possibilities
But I don't know how to start
doesnt this imply both must be having 5 as a factor
because otherwise you dont get 10 as the sum
3 and 7 already taken, and 2 + 8 isn't possible
But you can use 3 for the first integer and 7 for the second integer
it can also be
2, 3, 5
hmm I guess that's possible 
wait
the sum of the prime factors is including both right?
@proven zephyr Has your question been resolved?
Do we consider the distinct prime factors or count them as many times as they appear in factorisation of a number?
Okay.
But if other number had 2, would that count as separate?
Okay.
@proven zephyr Has your question been resolved?
Are you certain that there is an answer? I think i ruled out almost all of them. Of course, i could have made a mistake.
Anyway, confirm if there is indeed a solution.
Yes there is i found one on the internet
But i can’t understand it
wait
i will translate
Sum of other prime factors would be 7. Right?
I can't see any possibility other than (2+5) or (2+2+3).
Both of which are not possible.
oh wait i did a typo
😐
but yes
i wrote it as 17 - 7 - 3 = 10
edited tho
_ _
For example:
the two numbers are (x, y)
x = 7m
y = 3n
since the difference is 10 and x>y
then:
7m - 3n = 10
the values of m and n can be determined by reversing Euclid's algorithm
7 = 2×3 + 1
1 = 7 - 2×3
10 = 70 - 60
thus obtained
m = 10
n = 20
Thus, the general solution
m = 10 - 3t
n = 20 - 7t
x = 70 - 21t
y = 60 - 21t
The satisfying pairs of two-digit numbers are ={(28,18),(49,39),(70,60),(91,81)}
Note that the sum of all prime factors of x and y is 17, hence 17=3+p+q+7.
Then p+q =7, so the only primes p,q that satisfy are 2 and 5.
So, it is clear that among the pairs x,y, the only ones with prime factor 5 are x=70 and y=60. So, the sum of these two numbers is
x+y = 70+60=130.
i don't understand how they got m = 10 and 20 = n
Or you told me wrong.
Here.
Okay I'm not sure now.
According to what you said, there is no solution.
Hm.... okay, maybe it doesn't count as separate.
Other than that, approach is really simple.
You see that GCD of 3 and 7 is 1.
That means there are infinitely many numbers of the form 3n and 7m such that 7m - 3n = 10
Now, you just solve that using euclidean or diophantine equation.
You get general solution as m = 10+3k, n = 20 + 7k, where k is any integer.
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forgot to react mb
Do you want me to show what i mean by euclidean method?
It's just reverse GCD process.
Sure, if you're okay with it.
I'm not sure i've learnt it.
I'm pretty sure you have. At least the forward part.
So, we calculate GCD of 3 and 7.
$$ 7 = 3\times 2 +1 $$
$$ 3 = 1 \times 3 + 0$$
Enemagneto
I can see that GCD = 1
But what is this for?
I-
last time i did that it was at 4th grade
ima just go and relearn this after this
Sure.
Also, learn how to represent GCD of a and b in the form ax + by, where x and y are integers.
That's all it is about.
Okay!
Btw, an you continue with the explanation? I'll go back understand it after I've learned about it.
Okay. So, basically you try to find such two numbers m and n such that 7m - 3n = 1.
We know that there are such numbers because 1 is GCD of 7 and 3.
It's easy to see in this case that m = 1 and n= 2 works for us.
So, we have 7(1) - 3(2) = 1
but we need 7m - 3n = 10. Right?
yes
So, we multiply this equation with 10.
We have 7( 1 * 10) - 3 (2 * 10) = 10
Which is just 7(10) - 3(20) = 10
Lucky for you, your answer is already there. 70 and 60. But i'll explain further for general solution.
So, once you have found one pair of m and n that satisfies
7m - 3n = 10, you can find all the infinite solutions of this equation where m and n are integers.
This is something you can also think on your own. Would you like to try or should i move on?
You can move on.
Alright. So, key to finding all the solution is to imagine that we'll have different m and n but the RHS will always be 10.
So, basically you can say that both the terms 7m and 3n are increasing/decreasing by equal amounts so that their difference stays equal i.e. equal to 10.
So, we have something like this:
(7m + l) - (3n + l) = 10
Our m and n are currently 10 and 20 respectively. Remember that.
okay
You can take any value of l here and equation will satisfy.
But if we take such a l which is divisible by 7 then we can factor 7 out from l.
So, we'll have something like:
7(m+ k) - (3n + l) = 10
So, you see - Here, we have kind of found another integer m' = m+k which will satisfy our equation. Only issue is that it's not our solution yet as we have not found a corresponding n.
So, think about how we can get n'. Well, for that l has to be divisible by 3. Then we can factor 3 out from it.
So overall, if l has 3 and 7 both as its factor, we will get new m' and n'.
Makes sense ?
Why does n need to have 3 and 7 both as its factor?
I fixed the typo.
Great.
So, l will basically have to have 21 as its factor i.e. l will be of the form 21k.
Now, we are almost there.
Let's put it in the equation.
(7(10) + 21k) - (3(20) + 21k) = 10
(7(10) + 7(3k)) - (3(20) + 3(7k)) = 10
7(10+3k) - 3(20+7k) = 10
Where k can be any integer.
So, m = 10+3k & n = 20+7k
Just for fun, let's try putting some value of k.
Any integer.
3
Okay
m = 19 & n = 41
7(19) - 3(41) = 133 - 123 = 10
So, you have found all infinite solutions.
Now, work on m and n as you need them to have your required factors.
Do I just test them one by one or is there a faster way? (Sorry.... I'm really bad with number theory)
Well, fun thing about number theory is that it's very intuitive and realistic. Who doesn't feel cozy with the simple natural numbers so hang in there.
I'll give you a few pointers.
Look at your numbers.
You have 7(10 + 3k) and 3(20+7k).
You already have 3 and 7. So, remaining sum is 7.
Two possibilities:
2+5 OR 2+2+3
But we don't count them as separate.
2 + 2 + 3 would be 5 no?
Since we're counting 2 once
Ah. Yes. Still in mindset of original wording of the question. Lol
Only one possibility. 2+5
That makes it way more simple.
So, either 10+3k would be divisible by 2, and (20+7k) would be divisible by 5, or other way around.
Now try to think of k values which will make that possible.
Should be easy?
So then I just test them one by one?

wait... all of those give correct answers?
so-
huh?
ima just take a random k like.. 40
7(10 + 3k) - 3(20+7k) = 7(10 + 120) - 3(20 + 280)
= 7(130) - 3(300)
= 910 - 900
Prime factors of 900: 2, 3, 5
Prime factors of 910 = 2 x 5 x 7 x 13 nvm
so just.... 0
okay
thanks
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can someone help me understand this
discrete math
I am struggling to understand the solution for case 2, mainly at why sqrt An + sqrt L disppear when they are showing the proof.
kittie, i have this help-10 covered
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how formal do you have to be?
wym how formal
i'm not sure i could type out a perfect natural deduction proof
but if you just need to reason you way to ~q with the premises
as long as i understnad we good
yes yes
no u
okay. so you want to somehow conclude ~q. the only premise with ~q in is is s v ~q. in order to get ~q from this, we need for ~s to be true
basically you can just reason backward, if you want
wait why do we need ~s for ~q to be true
you know that s v ~q is true. if you want this premise to force ~q to be true, you have to know that ~s is true. i guess you can also see this by noting ~a v b is equivalent to a --> b. so s v ~q is equivalent to ~(~s) v ~q, which is equivalent to ~s --> ~q
so if we know ~s is true, then we get ~q is true
since the only way for ~s and s or ~q to both be true is if ~q is true
damm im lost asf
pog yeah, you can use elimination
you know s v ~q is true, so if you know ~s is true, you can conclude ~q is true
via elimination
s V ~q
~s
shouldnt it be q instead of not q?
this is just saying for arbitrary premises p and q. ~q is an arbitrary premise
it would be better if they said a v b, ~a, therefore b
then you could say you have s in place of a and ~q in place of b
okay so in any case, if the premise has not in elim
then the conclusion is also not
got it
i dont need tto understand why fuck it, i got a test in 30 min
you could have something like (p --> r) v (q --> s --> t) and if you knew ~(p --> r), then you could conclude q --> s --> t
with elimination
pog. so, if we do the reasoning backward method, we want to know ~s is true in order to do elimination on b. to conclude f.
so we have to somehow get ~s from the premises
e. tells us that if we know ~p and r, we will then get ~s (by using modus ponens)
so now we just need to know ~p and r is true from the premises
does this sort of make sense so far
yes
pog. now a. tells us that ~p v q --> r, so if ~p is true, then ~p v q will be true (by generalization), so then modus ponens will tell us that r is true.
so in fact, we just need to know that ~p is true in order to know r is true (and therefore ~p and r is true, by conjuction)
c. tells us that ~t is true, and modus tollens on d. will tell us that ~p is true
yes
help me understand this
how does ~t being true
tell us ~p is true?
d. says that p --> t, and you know that ~t is true, so then modus tollens says ~p is true. or do you mean why does modus tollens work?
an example might help. it is true that if it is rainy, then it is cloudy. so rainy --> cloudy. if somebody tells you that its not cloudy, then you can use this fact to conclude that it is not rainy
this would be an example of applying modus tollens in a case where its more intuitively clear
yes got it
because if it were rainy, then it would be cloudy. but we are assuming its not cloudy
are u able to talk rn?
no sorry 
😦
next to my gf who is in a call
ill send u 5$ enough to buy her chocolate 😉
" yo babe if i talk with this guy, you get chocolate, deal?"
@timid silo you are breaking the rules here
so ~t will modus tollens d. into ~p. then this will generalize to ~p v q, which modus ponens on a. into r, so then ~p and r are true. conjuction gives ~p and r is true. modus ponens on e. tells us that ~s is true, and then elimination on b tells us ~q is true
would be writing our backward reasoning forward
am i?
sorry!
mod didnt say anything bout it yesterday
u got time for 1 more?
no because i assume its either going to be slowly telling you the answer again or we will run out of time before your test

use the process i've conveyed to you and your inbuilt human rationality to try to reason through the next one

"Do not offer money for doing homework assignments, and vice versa" this is not for doing hw, this is for teaching me
idk if its still breaking the rule
i feel like you just need much more practice doing these things to do well for your test
i can't help you enough in 20 minutes or whatever
did you do any on your own :o
nope cus i had more things to go over bahah
okay how bout this
ill do the next one
and u check it
sure
hopefully you can do at least one on your own before the test 
i believe in you
okie kinda stuck now
nice. so you have p and you want to get p and s in order to get t using modus ponens on c.
so you just need to somehow get s
there is only one premise that allows you to conclude s, which one is it?
~q --> u ^ s
pog. now you can specialize to go from u ^ s to s
yea, you have p from the elimination you did earlier, so you can do conjunction to go from p and s to p ^ s
then modus ponens to get t
ohh i can do that?
yeah
its called conjunction here
if you have p,q then you can get p ^ q
theres one on the table called specialization
if you have p ^ q, you can get q (or p)
you have u ^ s, so you can get s
yeah. then you're done
whaaa
fr?
shii so if i remember the table im gucci
i know these things intuitively but i might need to write down after i use it
on the test
you got p from elimination on a, and then you got s from specialization on u ^ s. so you get p ^ s by conjunction, then modus ponens p ^ s to get t
yeah
gotta know all the rules and their names i assume
part of being in a logic class 
idk probably not i don't wanna do tons of logic problems
bahahah
i already did that 1-2 years ago

Appreciate the help bro
Imma ace it
you can do it 
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I have to turn this expression in the from asin(bx+c), I know I have to use Addtion thereom , but I'm not sure how. I'm thinking of using sin(x-y) = sin(x)*cos(y)-sin(y)*cos(x) but I am not sure how
can you take a picture/screenshot of what you learned as "addition theorem"
is this correct ? i didnt replace sin at the end but i get another answer on photomath and the math solvers
its integral of dx/rad(144+x²)
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yo
How is this X less or equal to 3?
I know R\ makes (3) into [3], but does it also make the (->) into [<-]??????
-> means infinity
<-
@strong wigeon Has your question been resolved?
It’s say’s that x is real number inferior to 3 I think
@strong wigeon Has your question been resolved?
No bro its equal or less
But ty for attempting
its saying $x \in \mathbb{R} \setminus (3, \infty)$
Ves
Ves
and $x \in (-\infty, 3]$ if and only if $x \leq 3$
Ves
For me when I say inferior it’s inferior or equal
You Are right but im confused Why infinity went to negative
Also since that E symbol say X before
I think it means X must be 3 or less
Ok
it means that x is in R, but x is not in (3, \infty). the set (3, \infty) is the set of all numbers y such that 3 < y
so its saying that x is a real number that does not satisfy 3 < x
so that means that x satsfies x <= 3
and then thats the definition of the set (-\infty, 3]
in this case, but i don't think that's how you should think of it
you should unravel the definition of the set to see what its saying
How i think of infinity ?
Ok
Ty
it seems like your first thought was "if you have R \ before an interval with an infinity in it, then this is equal to an interval with an infinity on the other side". and this is basically always true, but its probably better to understand why it happens than to try to memorize this
👍
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Hi, I Had this question from a previous year test as im studying and im not sure if i got the right answer as the one filled in is wrong but no right answer is written.
using the digits0-9, find the number of natural numbers that are even, have distinct digits and are less than 5000
I got 1373
2* 8 * 7 * 4 = 448
2* 8 * 7 * 5 = 560
8 * 8 * 5 = 320
8 * 5 = 40
5 = 5
total = 1373
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