#help-17
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how do i proceed here
@unborn wadi Has your question been resolved?
<@&286206848099549185>
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can someone please help
i understand how we got the 0s
i do not understand anything else
especially this
shouldnt we do the integral from 1 to 4
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Try a u-sub
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Apertyx
i think these questions are separate
it s a new function each time
and each time you try to find C
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hello
,w apart[1/(x^4-x^2)]\
Looks like PFD is the way to go here
ohhh no
what lol
same approach
take -5 outside and its the same question
This is where i am at
I am lost at this part
I tried using another example explanation as a reference
I don't understand how this is done
in my case
isnt it easier without expansion?
for me it's easier expanding
Oh
u didn't do that way before
It's easy, just expand and factor in terms of x^n
x^(n-1) etc...
here -B=9, there is no x term in 9 so -A=0, no x3 term so B-C+D=0 and so on is the expansion way
if you expand you get this.
$-5 = x^3 A + x^3 C + x^3 D + x^2 B + x^2 C - x^2 D - x A - B$
Samuel
now u have x^3(A+B+B) etc...
so u get the equations
A+B+C = 0
A+C-D=0
-A=0
-B=-5
cascade solution
and finished
where did u get lost?
I don't get where all this x^3 stuff and letter arrangement is going
you have A + C + D + B + C - D - A - B
$\frac{-5}{x^4 - x^2}$
$\frac{-5}{x^4 - x^2} = \frac{-5}{x^2(x - 1)(x + 1)}$
$\frac{-5}{x^2(x - 1)(x + 1)} = \frac{A}{x} + \frac{B}{x^2} + \frac{C}{x + 1} + \frac{D}{x - 1}$
Samuel
with all kinds of different x's
$\frac{-5}{x^2(x - 1)(x + 1)} = \frac{x^2(x - 1) C + x^2(x + 1) D + x(x - 1)(x + 1) A + (x - 1)(x + 1) B}{x^2(x - 1)(x + 1)}$
yes
Samuel
Samuel
I wrote it differen't that's what is confusing me
this last step u understand?
which one
this
no
and this?
yes
Samuel
wait
shouldn't it be Cx^2(x+1)
i chose C/(x+1)
it's no problem
because i did from the begining and i chose it this way
so u expand and get this
ohhh does that - xa and b come from distribution?
yes
and now u rearrange and factor
to get this
$-5 = x^3 (A + C + D) + x^2 (B - C + D) - x A - B$
Samuel
ok
$\left{
\begin{aligned}
A + C + D &= 0 \
B - C + D &= 0 \
-A &= 0 \
-B &= -5
\end{aligned}
\right.$
Samuel
now u get the system of equations
and solve
$\frac{-5}{x^4 - x^2} = \frac{5}{x^2} + \frac{\frac{5}{2}}{x + 1} + \frac{-\frac{5}{2}}{x - 1}$
Samuel
ok
I think I have this
only thing is
I am still doing the distribution 💀
That takes a while
just some seconds
u can make the final answer like this
$\frac{-5}{x^4 - x^2} = \frac{5}{x^2} + \frac{5}{2(x + 1)} - \frac{5}{2(x - 1)}$
so you can take out the 5, and do the integral
Samuel
Okk that's after you get the values of each of the letters?
yes
Ok perfect
I'm pretty sure I got it from here
just need the derivitive and then that's it
Thank you
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Hello
I am unsure if you are still here but I am lost at one part
Can I get your help on this
you tried partial fractions right
hmm have you managed to figure any of them out
you should remove the -9 or -5 or whatever constant
just call it $\frac{1}{x^4-x^2}$
jan Niku
ok
okay so we write $\frac{1}{x^2(x+1)(x-1)} = \frac Ax + \frac{B}{x^2} + \frac{C}{1+x} + \frac{D}{1-x}$
wait but we don't have the values right?
jan Niku
values?
we dont know yet
ok
Ik i meant it as a number any number
sure
so you have options here, the more annoying thing to do is to create the denominator on the left but on the right
the less annoying thing is to multiply through by the denominator on the left
oh ok so I do that again?
if we do that we get $1 = Ax(x+1)(x-1) + B(x+1)(x-1) + Cx^2(x-1) + Dx^2(x+1)$
jan Niku
yeah I had that
what does that mean?
that we started with an equality
in terms of x
so, its true for any x
we can pick an x value
and they still must be equal
yes
no
jan Niku
what I did was distribute everything
painful
this is true for any x, so pick some x values
for example, lets pick x=0
ok
$1=-B$
jan Niku
this comes out
$1 = Ax(x+1)(x-1) + (x+1)(x-1) + Cx^2(x-1) + Dx^2(x+1)$
jan Niku
let me think hmm
hint is try to make 0 factors
$1 = 2D$ i think
jan Niku
every other term has a factor of (x-1)
$1 = Ax(x+1)(x-1) + (x+1)(x-1) + Cx^2(x-1) + \frac 12 x^2(x+1)$
jan Niku
what now
honestly that's kinda hard I don't understand that D part
we can go back
$1 = Ax(x+1)(x-1) + (x+1)(x-1) + Cx^2(x-1) + D x^2(x+1)$
we were here
jan Niku
yeah
$1 = A(1)(2)(0) + (2)(0) + C\cdot1^2 \cdot (0) + D 1^2(2)$
jan Niku
jan Niku
alright, were here
jan Niku
YESSIR
$1 = Ax(x+1)(x-1) + (x+1)(x-1) + -2x^2(x-1) + \frac 12 x^2(x+1)$
jan Niku
the A part seems tricky
can we clean this up at all
,w Collect[Expand[(x+1)(x-1) -2x^2(x-1)+1/2 x^2(x+1)]]
I would just fit them on the fraction
eh
Don't substitute them in
that's how I would do the other ones
just solve for each value and then replace them on that top part A/x + B/x^2.... etc
we just need A
yeah
i think you need to factor it
no matter what it's zero
lemme see
see i guess ultimately
$1 = Ax(x+1)(x-1) + (x+1)(x-1) -2x^2(x-1) + \frac 12 x^2(x+1)$
jan Niku
you see how A is in the x^3 term
yeah
well its $0=A-2+1/2$ i think
jan Niku
right 
what
,w apart[1/(x^4-x^2)]
OH
i missolved C, sorry
$1 = Ax(x+1)(x-1) + (x+1)(x-1) - \frac 12 x^2(x-1) + \frac 12 x^2(x+1)$
jan Niku
just with that this is the correct equation
yeah it should be -1/2
so heres the correct equation
$1 = Ax(x+1)(x-1) + (x+1)(x-1) - \frac 12 x^2(x-1) + \frac 12 x^2(x+1)$
jan Niku
okay, now by visual inspection, identity the coefficient of the x^3 term in the expansion
can you do this?
look for places where there are 3 x's in a product
A?
it looks like A will come from the first product
nothing from the second
we'll get a -1/2 x^3 from the third
yu[
so if we expand, well get $(A+\frac12 -\frac 12)x^3$
why is B missing?
jan Niku
only a quadratic factor
it originally had x^2 in the bottom
Ah ok
so when we multiplied by x^2(x-1)(x+1) we only had that left
so heres the expansion
have you done matching coefficients before?
method of undetermined coefficients sometimes called
not sure tbh
it works like this
Just got one lecture on this
say 1 = a + x
think about this like ...
$1 + 0 x^1 = a + 1 x^1$
since this has to be true for each x, each coefficient must match up, power to power
because a constant term cant equal an x term
and an x term cant equal an x^2 term
not for all x at least
so if you have something like 1 = a + x is true for all x
oops i fudged it 
should be 1 = a + Bx
the point is
theres no x on the left hand side
so there cant be one on the right hand side
then B must be 0
did i lose you 
yeah
the point is, we can say $A + \frac 12 - \frac 12 = 0$
jan Niku
okay forget the example i just fudged
if $4 = A + Bx$ for all x
whats A and B?
solve by inspection
jan Niku
A = 4-Bx
dont use algebra
oh
just use your reasoning
4 cant change right?
i mean, 4 will always be four
it cant change depending on x
yes
and its equal to the right hand side
so, the right hand side also must not be able to change with x
otherwise, it will move away from 4
if $4 = A + Bx$ for all $x$, then $B$ cant be anything but 0
jan Niku
kinda
its really just like
find the linear function thats always 4
well, it cant have any slope but 0
it must just be a flat line
I see
jan Niku
jan Niku
and we just equate coefficients
x^3 terms must have the same coefficient
same with x^2, x, constant ...
if you by we can do this then youre basically done
$1 = Ax(x+1)(x-1) + (x+1)(x-1) - \frac 12 x^2(x-1) + \frac 12 x^2(x+1)$
jan Niku
we can go back here, and just pull off the x^3 coefficients of each side
on the left, its 0, and on the right, its A - 1/2 + 1/2
equate them, and get A=0
ahhh ok
then, you just check your work with a robot
Ok I think I can figure this out i'm close
,w Apart[1/(x^4-x^2)]
Thank you
np
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Take those last two equations you got, 2y-5z=-6 and 5y-9z=-15 and solve them for y and z, ignoring the rest of the equations. Once you get answers for y and z, you can plug them both into any of the three original equations to get x
bro....
HOW
HOW DO I SOLE FOR Y OR Z
IM SO LOST
ah sorry, didnt realize that was your question. it gets taught in different ways, usually called substitution or elimination. I'll do it with substitution since the previous part uses it.
Take the first one and solve it for y. Start by adding 5z to each side to get 2y=5z-6, then divide each side by 2 to get y=(5/2)z-3. Plug that into the second equation to get 5((5/2)z-3) - 9z = -15
Do you know how to solve that last one for z?
we cant put decimals or fractions in there
we would plug in formula for y into z right
Yeah, that's what I did at the end, 5((5/2)z-3) - 9z = -15 only has z so it's just one variable we can solve for
And I think the work is going to involve fractions, but you end up with whole numbers
I don't see a way to avoid fractions as part of the work here
5((5/2)z-3) - 9z = -15
(25/2)z - 15 - 9z = -15
(7/2)z-15=-15
(7/2)z=0
z=0
where the hell did the -9z go
right
after we do (25/2)z - (18/2)z, we get (7/2)z
Oh ok sorry if you already got that
it equals 0
Yeah after you add 15 to each side you just get 0 anyway
so the fraction doesn't matter I guess anyway
But yeah now that we know z=0, we can plug it back into one of the two equations with just z and y to get y
i got x = 2 y = -3 z = 0
Yep, that's the answer
bro i love u ive been on this problem for hours
haha happy to help
@steep jackal Has your question been resolved?
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hi
Idk how to answer those question
I mean i think i do
im just not confident if im doing it right
How far did you get? It makes sense to me to start by noticing the triangles are similar by AAA. Then use Pythagorean Theorem to get AD. Then use similar triangles to figure out AE, then do AE-AD to get DE.
Right, I kept it as 8.33 but rounding down to 8 can be fine depending on how the class is taught
For AE, we need to use that the triangles are similar
I set up the equation 3.4/4.9 = 8.33/AE and solved for AE
(since with similar triangles, the proportions of the corresponding sides are the same)
i got approximately 12
if i subtract 8 from that then is DE 4?
that sounds like a dumb question but
is that the correct answer
Yep, that's right!
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what do i do next
eliminate x or z
hiuh
like how you eliminated y
yes.
so you went from 3 equations and 3 unknowns
to 2 equations and 2 unknowns
which you probably have solved before
idk what y is either
im use to subsitution
idk how to do elimination hep me plz
This algebra video tutorial explains how to solve systems of equations by elimination and how to solve systems of equations by substitution with 2 variables.
Systems of Linear Equations - 2 Variables: https://www.youtube.com/watch?v=oKqtgz2eo-Y
Systems of Equations - Fractions & Decimals:
https://www.youtube.com/watch?v=jlddJQ1qYDU
...
elimination is when you multiply two equations in a system of equations so that they have the same values
and then you add the two equations together
but one has a positive and one has a minus so if you added it, the answer would be zero, hence eliminating that variable
im listening
well
for example you have
x + y = -3
-3x + 3y = -9
say u wanna find the y value
then u would need to eliminate x
if you have x and -3x, you could multiply x and 3 to get 3x. then u could add (3x) + (-3x) to get 0
you feel me
no
ok can i give u a step by step example
idk how to get rid of x or z rn
5x+13z+7
6x+11z=13
multiply both of them by different things to make it line up
those are ur equations?
ok which one are u supposed to find, the variable of x or z?
all
nah wtf
find z first (by eliminating x)
have fun lil bro hayley got u
then use that value of z to find x
then use those values to find y
watch that video
OH
ok so for example if you wanna eliminate the x variable
the coefficients of the x variables are 5 and 6
so youre gonna multiple both equations to GET the lcm (least common multiple) of 5 and 6
in this case it's 5 * 6 = 30 = lcm
so you're gonna aim to change 5x and 6x into 30x and 30x so that they are the same so that you can eliminate them
to do that, multiply the equations:
6 ( 5x + 13z = 7)
reason for doing that is because 6 * 5 = 30
and then:
5 ( 6x + 11z = 13)
so ur gonna have:
6 ( 5x + 13z = 7)
5 ( 6x + 11z = 13)
multiply those two equations by each other and then tell me what u get
and ping me i guess 😭
did u multiply them yet
-30x-78z=42
good
30x+55z=65
good
now thats ur system of equations
-30x-78z=42
30x+55z=65
now just eliminate by using addition
the 42 is negative
okay
its 22
z = 22?
23z=22
oh
-30x - 78z = -42
30x + 55z = 65
i didnt
ye
facts
holy
youre gonna repeat that whole process to find x using these two equations
then once u find x
youll know the values for x and z
then you can use those to plug it into the og equation which is 2x + 3y + z = -2
then u can find y through that
then boom x y z
holy crap im so smart too
ping me if u need any more help
@steep jackal Has your question been resolved?
it was wrong
did u find the right x value
-11 ( 5x + 13z = 7)
13 ( 6x + 11z = 13)
-55x + -143z = -77
78x + 143z = 169
23x = 92
x = 4
i think you keep mixing up the symbols which leads to error so you have to keep double checking
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I dont know what i am doing wrong
can you show how you got that
so the geometric series i represented it as is a_n = 4(-1/2) ^(n-2) and I basically did the summation from n=1 -> infinity minus n=16 -> infinity
because we want n=1 -> 15
cuz when u do the summation of n=1 -> 15 it gives the series on the pic
um i started it at n = 1
oh i see
i just started with the 4 and then subtracted the 8 at the end haha
should be equivalent either way
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how do i do this
do you know how arctan behaves for large arguments?
so one could say [\lim_{n\to\infty} \arctan (2n) = \frac{\pi}{2}]
maximo
does it?
yea...?
then why are you asking me
im making sure
"test for divergence" aka the terms don't converge to zero?
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hello i am programming a compass for my smart watch
the compass "image" is rotated on the watch to suit its orientation
the value for the orientation is derived in 3 steps
- obtain magnetometer reading in radians (this gives a range of +/-π)
- convert radians to degrees (this gives a range of +/-180)
- remove any negative values from the range
step 3 is where i am getting stuck
if i use(heading + 360) % 360then north/south is displayed correctly, but east/west is reversed
i believe this is due to my compass rotating clockwise, however i am not very good at math :<
any and all help is appreciated :)
wait so is the magnetometer reading offset from north? so if it gave pi/2 that would be east, and -pi/2 would be west?
i will get you the docs, one sec :o
by removing do you mean setting it to 0?
no i mean offsetting the range so its lowest value becomes 0
well so how about (heading < 0) ? 180 - heading : heading
ah ty
ok
wait what is the required output?
ohhh
the required output is 0 = north, 90 = west, 180 = south, 270 = east.... i think >.<
wouldn't it be 90 = east?
my mind is on fire o.o
your output is counter clockwise the magentometer value is clockwise
no i'm right, let me show a picture
:D
so -1 -> 359, -179 -> 181
so it would just be 360 + x
so (heading > 0) ? heading : heading + 360
if you are using a language that supports the ternary operator
i'm using kotlin :o
oh ok
so if i'm facing north the reading is 0 and no rotation is applied to the image
if i'm facing east, then the image needs to rotate 270 clockwise so that east is on top of the watch
if that makes sense >.<
wait a second thats wrong
D:
my answer
oh
-x if x is negative, else x + 180, if i understand kotlin correctly after 1 minute of learning about it that would be (if (heading > 0) heading + 180 else -heading))
i think i understand that expression :D
i'm not sure if kotlin would accept it... but i understand it :D
waaait a second that might be wrong
oh no :o
according to kotlin docs its right
i'd be embarrassed if you outpaced my 3 days learning kotlin in one minute xD
i understand a lot of programming
:D
i just looked up the equivalent to my python
wait a second so its like this: 0 = north, 45 = northwest, 90 = west, 135 = southwest, 180 = south, 225 = southeast, 270 = east, 315 = northeast
well -x if x is negative definitely, else it would be 360 - x?
so it would be if (heading < 0) {-heading} else {360 - heading}
try that and see if it works
ok :D
it wooooorks!!!!

it finally works after 3 days of staring at my IDE
thank you so much!!!
♥️ ♥️ ♥️
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Let n be a positive integer. Let S be the set of all subsets of [n] = {1, 2, . . . , n} that
contain the element 1; let T be the set of all subsets of [n] that contain the element n.
Define a bijection between S and T, and find its inverse. So- I've come up with an idea abt the bijection - but I'm unsure abt the inverse portion
@alpine sparrow Has your question been resolved?
what have you got for the bijection S->T?
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hey guys, how the hell do i prove this thing
i tried and im getting weird answer
and yes i did use the cos a cos b thing
getting me nowhere
try writing the cos angles in sin
write and give feedback
just write it and you ll understand
ok
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(n+1)^(n+1) = (n+1)^n * (n+1)
so you can do something with (n+1)^(n+1)/(n^n)
and then n!/(n+1)! = 1/(n+1) clearly
so i don't change the part of (n+1)^(n+1)/(n^n) ?
you can rearrange it into something
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can anybody help me simplify this problem with formulas
is i the complex number √-1 ?
first u expand the brackets then multiply with conjugate to make the denominator real
Also is the , for decimal?
Okok
i did it multiple times but everytime i get big big numbers
may i see what u have tried
its a bit messy but seems like something is wrong with ur arithmetic
did u verify each step with a calculator?
cuz ur method is completely correct
but ur final ans is wrong
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i think it is wrong
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The equation
[x^{10}+(13x-1)^{10}=0,]has 10 complex roots $r_1,$ $\overline{r}_1,$ $r_2,$ $\overline{r}_2,$ $r_3,$ $\overline{r}_3,$ $r_4,$ $\overline{r}_4,$ $r_5,$ $\overline{r}_5,$ where the bar denotes complex conjugation. Find the value of
[\frac 1{r_1\overline{r}_1}+\frac 1{r_2\overline{r}_2}+\frac 1{r_3\overline{r}_3}+\frac 1{r_4\overline{r}_4}+\frac 1{r_5\overline{r}_5}.]
Dork9399
!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 was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
notice its basically asking for the sum of reciprocals of magnitudes of roots
yea
By P you mean the polynomial, right?
yes
hmm
Can you explain what you mean by this?
a root satisfying f(x) = 0 means f(r) = 0, if we consider g(x) = f(1/x), then 1/r satisfies g(x) = 0
Ah yes, that makes sense
We can also let,
[u=13x-1,]then we can write the equation in this form [(u+1)^{10}+(13u)^10=0.]
But how would I find f(1/x)?
Rather, how would I find those roots?
if you replace x with 1/x and cross multiply by x^10 to clear out the denominator, you should see a relation to the roots of unity
So I got $\frac{1}{x^{10}} + (\frac{13}{x} - 1)^{10} = 0$
Dork9399
So $1 + x^{10}(\frac{13}{x} - 1)^{10} = 0$
$ (13x- 1)^{10}= -1$
Dork9399
Dork9399
Dork9399
this does work as long as you realise the 10th root is multivalued
so you don't miss out on solutions
yep
and we know that the magnitude of all of the tenth roots is 1
its 13 - them though, so it's not quite that simple
in essence you're just evaluating $\frac{1}{2} \sum_{k=0}^9 |13-r|^2$
AlphaNull
where r is a root of this
the reason for the 1/2 is because we only care about 5 roots (since the roots and their conjugates come in pairs)
Yea that makes sense
But how would I evaluate this?
Wouldn't that require finding the real and imaginary parts of 13-r?
@lucid crypt
i think there is a more clever way, let me think about it
adding up conjugates seems to yield nice sums but its still not as nice as i would have hoped
$12 + 14 + \sum_{k=0}^4 (13-r)(13-\overline{r})$
AlphaNull
12 + 14 comes from the 1 and -1 roots respectively
the sum is just the problem evaluation
since 13-r and 13-r conjugate are just roots of unity, you can probably try to represent them as $e^{i 2 \pi k / 10}$ and expand it out
AlphaNull
it's not something i'm too excited to do
Wait but 1 and -1 aren't tenth roots of -1
The only thing you can cleanly evaluate is for i
@lucid crypt
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isnt |i-13| sqrt170?
im not sure why im adding them actually,
it should just be $\sum_{k=0}^4 (13-r)(13-\overline{r})$
AlphaNull
i dont think there needs to be a 5 since 0 to 4 already accounts for 5 solutions,and conjugates come in pairs
1 to 5 should work
or no nvm
just 0 to 4
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should one of my intervals be around when x = 0 for the no solution in the second screenshot? bit confused about that
It’s saying that 1/x^2 never equals zero
For any real value of x
So you can just ignore that term as not having a zero
At x=0 that term goes to infinity
alright, so if a factor when finding critical values is say... ( 2/x ) then...in that case i would have a critical value of zero?
i vaguely remember there is supposed to be a situation where i have an interval when i find undefined terms somewhere
No just look for the roots of the derivative the points where the derivative is 0
Those are your critical points
The critical points are where your maximums or minimums are
Then using those you can create intervals to determine if they are in fact maximums or minimums
alright, this sounds like the solid definition that i was confused about
could you explain what my course was trying to teach then when they mentioned this part where it says the critical number is so and so does not exist
Well if the derivative does not exist then it’s also critical graph the function |x|
There’s a sharp turn at x=0 meaning that there is no derivative there
But it’s still a minimum of the function
i never thought of this, or dealt with it and im already into solving second derivative problems 😭 its like there are so many holes in my education
thanks for the help on the other part though 🙂
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I need help to find the median, mode, and range of this, not sure what to do
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I use discriminant
and factorise to (k+4)(2k-4)
is this right?
and then i do k <-4 or k<2
wdym
not sure how you got there
b^2-4ac<0
💀
64 - 8(k)(k + 7) < 0
mb
you put it as 28
oh shit yeah
i forgot to to times the 7 by two as well lmao
ok thanks
ig thats why i got it wrong
ill ask gpt to factorise with the correct expression this time
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np
k<-8 and k<1?
u mean i change or for and?
mysolution is coming diff than yours
theres no way that can be right?
ur factorising this right?
🙈
wouldnt this still lead to the same answer tho
it would
im p sure both are correct
j u divided through
gpt didnt
and i was too lazy to do either lmao
chatgpt got the correct answer
ok cool
this is the wrong part
wait how is it wrong tho
k<1 not k<-1
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Stuck with this:
I know g(x)=1/1-x is of order 3.
So I let y=g(x)=1/1-x and z=g(g(x))=x-1/x.
Then y=g(x)=1/1-x, z=g(y)=1/1-y and x=g(z)=1/1-z. So my original equation becomes f(x) + f(y) = (2(1-2x)/x(1-x))
I am now lost and very sorry for poor formatting im very new to this
Pls I hate functional equations
<@&286206848099549185>
@south fox Has your question been resolved?
@south fox Has your question been resolved?
still available?
Yes I still need help pls
working on this wait
just check it i am not sure if i am correct so just check it
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Can someone help me with this please? i don’t know what i am doing wrong
What happened with this one?
Like 1/(a-2+b), so the entire a-2+b is in the denominator?
