#help-39
1 messages · Page 113 of 1
This essentially means $x= 1 \cdot x$
ƒ(Why am. I here)=I don't Know
maybe something along the lines of if d | x then d = x or d = 1
ƒ(Why am. I here)=I don't Know
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like this?
Remember you're making a claim about x (that it's prime), rather than [trying to/] say[/ing] "primes exist"
mhm
Also "what's d?" 
right
a divisor
of x
hmm
so what exactly is wrong with my statement?
It's just a convolted way of saying primes exist?
it's not well formed
ƒ(Why am. I here)=I don't Know
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$\exist x( x= y \cdot z \land y \neq z\land ( y \vee z =1))$
ƒ(Why am. I here)=I don't Know
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you need to introduce d here
the statement that "x is prime" depends on x, so you don't need to introduce x
I see, so just there exists a d such that d|x...
ƒ(Why am. I here)=I don't Know
is that how you tell a number is prime?
9 is prime because there exists a number d=9 such that 9 | 9, and 9 = 9
that's not true is it
yes
uniqueness of prime factorizations applies to all integers > 1, not just primes, as per the fundamental theorem of arithmetic

$\exists d(d|x \land (d=x \vee d=1))$
is this it?
if not could I have another hint ? 
a number x is prime if the only divisors are x and 1
yes
here, you're only testing that fact for a single divisor d
ƒ(Why am. I here)=I don't Know
go back to this
this was on the right track
$\exists d( d|x \implies d=x \vee d=1)$
the problem is that you've only asked for a single d to satisfy this
I don't follow, I just enclose the 2nd part in brackets and I'm done, right?
for x to be a prime, any divisor of x must satisfy the condition in the right
so I introduce another variable similar to d
no
you quantify over d with a universal quantifier
every divisor of x must satisfy the condition
$\exists d( d|x \implies \forall ( d=x \vee d=1))$
ƒ(Why am. I here)=I don't Know
no thats not well formed
and what i mean is
$\forall d( d|x \implies d=x \vee d=1)$
every divisor of x must satisfy the condition
yes, I get that bit, but I'm not sure of how to write it
isn't that what I;ve written here?
no that expression is not well formed
the forall doesn't have anything it's attached to
how would I do that
ah, I see
because you want to make a statement about all divisors of x
not just some particular one of your choosing
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im not sure how to do this
i do know that i have to calculate gpe and ke
but my topic doesnt have any formula for friction and im not sure how to minus off my friction so well kinda need some help with the friction
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!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
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how would you determine if a subset is closed under addition and multiplication comprehensively
for addition: define two arbitrary elements of the set, noting that they satisfy the condition of the subset. find out whether their sum necessarily satisfies the condition as well
the specifics depend on how the subset is defined
your lecturer combined the addition and multiplication closures into one expression
yeah he said it is an alternative subspace test
so to show it's closed under addition, we need f1 + f2 to belong to the set, and for it to be closed under multiplication we need λf1 to belong. so λf1 + f2 is in the space if and only if the previous two conditions are met
yeah that makes sense
he only also proved the non-existence of the non-empty set by showing that the 0 vector of the vector space V is also part of the subspace S
0 is a convenient vector to check since if it is not in the space then either:
- the subset is empty
- the subset is not closed under addition and scalar multiplication
makes sense
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The table shows three values of x and their corresponding values of y, where y = f(x) + 4 and f is a quadratic function.
What is the y-coordinate of the y-intercept of the graph = f(z) in the Y-plane?
Ans: f(x)=-4(x-21)(x-25)-12. but why?
you asked this question more than 10 times
and you were answered each time
13
meow i love cats
I want to put it in the factored form.
@halcyon plank Has your question been resolved?
@halcyon plank Has your question been resolved?
@halcyon plank Has your question been resolved?
@halcyon plank Has your question been resolved?
@halcyon plank Has your question been resolved?
Can you explain what the previous methods explained to you were, and why they weren't what you were looking for?
because i want to understand the method I am pleased with.
That didn't really answer my question. I'm trying to get enough information to help you, but I can't really help if I don't know what you're looking for and what's already been explained to you.
Oh
I was taught the vertex form quadratic equation
and basically graphing points on a graphing calculator
i was also taught the factored form quadratic equation but surprisingly i couldn't understand it, so just like u can see lol. im trying to understand it
I think the answer you wrote has a typo. It should be -4(x-21)(x-25)-12.
Are you trying to figure out how to get from that answer into a factored form?
yes
Okay
The first step would be to expand everything out
So, you want to multiply (x-21) by (x-25)
Do you know how to do that?
Yes
Okay so then what do you get
We do if we want to figure out how to factor it
Okay good
Next we need to multiply by -4
So that gives us -4x^2 + 184x - 2100
And finally subtract 12 and we get
-4x^2 + 184x - 2112
but why do we subtract by 12
do you mean why do we subtract by 12?
yes]
It's because there's a - 12 in the original answer we got
See here ^^
but i dont understand it
like why is there a -12
Are you asking why the answer is -4(x-21)(x-25) - 12?
no
kinda
im only asking why is there -12
i understand from where do the other terms come
but not "-12"
here's where i'm confused
OK so let's try seeing what we get without the -12
okay
So, f(x) = -4(x-21)(x-25)
Our equation is y = f(x) + 4
So that gives us y = -4(x-21)(x-25) + 4
And now let's try plugging in our values of x=21, x=23, x=25
okay
If we plug in x=21, the first term becomes 0, so we get that y = 4
Same with if we plug in x=25, we get y = 4
Does that make sense
okay
no
What part doesn't make sense
yes
Okay so
Also if we plug in x=23, we get 20
So we can make a table of our results
x y
21 4
23 20
25 4
If we compare that to the table that we want
x y
21 -8
23 8
25 -8
You can see that we're off by 12 each time
4 - 12 = -8
20 - 12 = 8
4 - 12 = -8
So we need to subtract f(x) by 12 in order to get the table we want
okay
is there a shorter way to reach that step?
We're just plugging in numbers and then comparing them with the numbers in the table we want
okay
I explained it in detail to help you, but the actual method is pretty short
Once you get used to it
tysm
Np
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hello
ok
$$\frac{5}{7} \cdot \frac{a^{11}}{a^7} \cdot \frac{1/b^8}{1/1} \cdot \sqrt[3]{2^3 \cdot 3^3 \cdot 3^2 \cdot a^2 \cdot b^{18}}$$
Mr. Gamer 🇵🇸
is that right
yes
alright i'll let another helper take over because i'm gonna be hungover
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let $f(x) = \frac{24e^{x}}{3e^{x} + 1}$ find the range of f
938c2cc0dcc05f2b68c4287040cfcf71
,, \lim_{x \to +\infty} \frac{24e^{x}}{3e^{x} + 1} \= \frac{24}{3}\lim_{x \to +\infty} \frac{e^{x}}{e^{x} + \frac{1}{3}} \= \frac{24}{3}\lim_{x \to +\infty} \frac{1}{1 + \frac{1}{3e^{x}}} = 8
938c2cc0dcc05f2b68c4287040cfcf71
,, \lim_{x \to -\infty} \frac{24e^x}{3e^x + 1}
938c2cc0dcc05f2b68c4287040cfcf71
are you sure the question is to find the range of that function
right now all youre calculating are limits
you dont use limits to find the rnage
yeah that sounds like they're probably asking for the range
the english word image and range are interchangeable
okay
when you get to higher portions where the preimage or domain no longer mean the same thing, a distinction appears
okay
you can start at the range of e^x being (0, inf) and build up the function
that can be used if you only have one e^x in the function
the range of $y=e^x$ is $(0,\infty)$
not "0, inf", (0, inf)
why doe
mtt
,w range e^x
the (0, inf) is interval notation
the open interval, "all numbers strictly greater than 0" ("up to infinity" meaning no upper bound)
it is short for "0 < something < infinity"
never no
can you raise e to a power
u cannot
and get a negative number?
that is what range means
remember youre only working with real numbers
ln(-1) is ambiguous and is also not real
please pay attention
are you paying attention right now?
I need a yes
yes
the range of e^x is believably (0, inf), right?
sure
can you elaborate on whats holding you back from completely believing it
nothing
using "sure" instead of "yes" is usually meant to mean "I see that you want me to believe that" and doesnt actually show whether you understand or not
yea dw
so what?
you can start at the range of e^x being (0, inf) and build up the function
that can be used if you only have one e^x in the function
right now theres two e^xs so its not immediately useful
but theres an easy way to reduce the number of e^xs there are in the function to one
,, f(x) = \frac{24e^x}{3e^x + 1}
938c2cc0dcc05f2b68c4287040cfcf71
can you find that easy way?
well
$\frac{24e^x}{3e^x + 1} = \frac{24e^x}{3e^x + 1} + \frac{24e^x}{3e^x + 1}$ is this legal
is $\frac32=\frac31+\frac31$?
mtt
nope
then no its not legal
I messed up
if you want to split the fraction into something that cancels out nicely, you need to consider the entire denominator
see if you can get some version of a 3e^x + 1 in the numerator
right now it says 24e^x
8(3e^x + 1) - 8 = 24e^x you mean
its alr
now what
put that in the numeraotr
okay
then see if you can simplify f
,, \frac{8(3e^x + 1)-8}{3e^x + 1}
mb
938c2cc0dcc05f2b68c4287040cfcf71
938c2cc0dcc05f2b68c4287040cfcf71
thats correct
😎
now with one e^x, you can start from "the range of e^x is (0, inf)" and apply each calculation that f does to the range
for example 1 + e^x's range is (1, inf)
bruh
did you figure it out yourself or did you just use wolfram alpha to give me that answer
wdym different one? I usually do this shit using limits ngl
you gotta ask when you dont understand something
forget this
we're doing something completely different
you arent even looking at what I suggested to you
I mean
you said
e^x range is 0,inf
- 1
1, inf
then multiplied by 8
8, inf
then?
first off
this is your function
you are not finding the range of 8 (e^x + 1)
second off
not a single word abotu this until after I look like Im dropping the idea entirely
sorry
surely its not an exclusively english idea to you to say when you do something
you believe this?
0,uif
what is the range of 3e^x + 1
1,inf
what is the range of 8 / (3e^x + 1)
💯
@stoic imp are you stuck
lowkey yeah
okay
say you have a number between 2 and 4
and you take its reciprocal
that number then is between 1/4 and 1/2, right?
reciprocal is an english term for doing 1 / (something) or (something)^-1
flipping is ambiguous and should not be used
thats not ideal
you dont need to convert 1/4 and 1/2 to decimals to understand what Im going to say
okay
now say you have a number that is at least 127
no not like that
Result:
0.0078740157480315
no
Im asking if youre familiar with the fractions 1/2 and 1/4
instead of reading them as a weird way to write a decimal
okay
this is taking too long, you can ignore that question
say you have a number thats 127 or higher
and you take its reciprocal
the reciprocal is between which two numbers?
can i respond with unsure
say you have a number thats between 127 and 131
and you take its reciprocal
the reciprocal is between which two numbers?
127^-1 and 131^-1
y
I gotta break it to you but "y" is ambiguously "yes" or "why"
this number here doesnt have an upper bound
think about its reciprocal
its positive, rightg
its also below 1/127, right
+inf, 1/127
now you gotta be careful with what youre saying there
can you repeat the two numbers the reciprocal is between?
how did you guys get to this point
127^-1 and 131^-1
127 or higher here
that means it can go lower than 131^-1
okay
right
it cant be 0 either, right?
right
(0, 1/127]
0 < reciprocal < 1/127
now ?
writing $f(x)$ as $8-8\cdot\frac1{3e^x+1}$,
mtt
(0, 1]
(0,8]
wait
slight difference here
here I included 127 so the reciprocal could go up to 1/127
but here 1 cant be included
so 1 is left out
whoops
so the range of 1 / (3e^x + 1) is (0, 1)
(0,8)
(0,1)
...whats the range of 8 * 1 / (3e^x + 1)
(0,8)
so whats the range of 8 - 8 * 1 / (3e^x + 1)
unsure
if you have a number from 0 to 8
and you subtract it from 8
what numbers would it be between
-8,0
mb
8 to 0
sure
the range of 8 * 1 / (3e^x + 1) is (0, 8)
so whats the range of **8 - **8 * 1 / (3e^x + 1)
8 to 0
how would that work
or finding the domain of the inverse
neither this or the other one reliably works
reliably
no but
usually its better to know where the asymptotes are to find the range quicker no?
would it work for 1 / (1 + x^2)?
by doing a sketch of the function
you dont define functions by their asymptotes
I was referring to finding the range
what?
how does that go against what I said? youre implying I didnt know you were doing that?
so?
well
its not necesary to know about the asymptotes to find range
this gives you some slight confirmation on what you found but can be overridden
so in terms of that its not very good confirmation
the asymptote can at least guarantee that the range should include a (asymptote or asymptote) in at least one interval
you should repeat the ()s
you found that as x -> inf, f(x) -> 8
this tells you that the image should have a 8) or a (8 somewhere
yeah
the image of f(x) is (0, 8) which we found without ever caring about the asymptotes
okay
you can see there the 8) as suggested by the asymptotes
but that is only vertical asymptote we still need to find horizontal and oblique asymptotes before we find range
x -> inf is not a vertical asymptote
that is horizontal mb
now you do have something neat if you look for vertical asymptotes
if you have a limit that -> inf or -> -inf,
x -> something, f(x) -> inf would confirm a inf)
sure
x -> something, f(x) -> -inf would confirm a (-inf
that sounds like a lot of work for asymptotes that we ultimately dont need
if you do find an oblique asymptote, it still fits what I said about vertical asymptotes
alr I gtg
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what am I doing wrong here
not sure what you're doing but think of (n+1)! as a single chunk of which you have 1 and n+1 of
How did you get this? The rest is correct
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How do I simplify this/ what do I do next?
first of all you can simplify f(t)
(6t+18)/(t+7) = [6 (t+3) ] / (t+7) = (6(t+7) - 42 + 18) / (t+7) = (6(t+7) - 24)/(t+7) = 6 - 24/(t+7)
How do I get that?
Does this work?
do you know quotient rule?
i assume yes since theres lims
I think I have it in my notes
LMAO
oh wait yeah you can simplify it
thats probadly easier than this
but this should work just fine
lol
so what do i do 😭
Quite Peculiar
either works
so what I did works?
oh idk what you did
i meant quotient rule or differntiating that guys simplified form
thats fine
what did you do here?
am i misunderstanding the question or are you not supposed to just differntiate it
and thats it
uh
like
f(t) = 5x^2
f'(t)=10x
like that?
whats this btw
is a just a value
or something else
im doomed
all i know is dy/dx
😭 im so screwed for my exam on saturday
you got time
go watch a video from organic chem or khan academy
its not that complicated
i'll go do that and be back in the morning
Writing it as
[ 6 - \f{24}{t + 7} ]
might make it easier for you
neon
I see
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The reflection of the plane P1:2x−3y+4z−3=0, in the plane P2:x−y+z−3=0, is the plane ?
@midnight haven Has your question been resolved?
<@&286206848099549185>
Considered a random point on the plane 2x-3y+4z-3
(-2,-1,1)
found the image of the point wrt to the plane x-y+z-3=0
${-2+2sqrt3,-1-2sqrt3 ,1+2sqrt(3)}$
Cnidarian
this point did not lie on neither A nor B nor C
so I choose D
i was wrong
This is what i did
2 min i will check
:p
i used the wrong formula
I always forget that the sqrt doesn't exist
thank you!
got it
.close
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is $k^m$ called "algerbric field"? and what does it equate to?
Ayanokoji
no you'd call it a vector space
in your picture the elements are being denoted with column vectors
Why?
its just what people call it
But a vector space is not just a set of vectors
It also needs a set of scalars and a binary operation
it doesnt matter if it's a column vector or a row vector, or does it?
K^m can be equipped with those operations in a natural way
thats just a matter of taste
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also it's a space because i can divide the vector space into a summation of different vectors right? v1(1,0,0,..)+...+v_n(0,...,1)
no, its a vector space because it satisfies the vector space axioms
(technically, you need to equip K^m with the vector space operations and then say that its a vector space but thats being pedantic)
alright, i think then this will be formally defined in a future lecture, ty mate
.close
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This seams to easy to be true <@&286206848099549185>
!15m
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How do I proceed with this? All I got was simplifying the numerator to (x^3 + 1)(x^3 - 1)
what is R?
real numbers
oky
consider: $x^6 - 1 = x^6 + 1 - 2$
ℝαμΩℕωⅤ
idk what to do after this though
oh wait
i can try long division
You could also trig sub and repeatedly use 1 + tan^2 x = sec^2 x
i had the sudden idea of doing [\frac{x^6}{1+x^2}-\frac{1}{1+x^2}] to get a -arctan term, but probably would lead to bad integration by parts.
fish
It'll only take like 2 iterations
how do i go about doing that
denom being this
with the route i suggested, you don't really need trig sub
if you want to do long division, just do it directly
the way i expressed it, a sum of two cubes identity can be applied to (x^6 + 1) which makes the division very simple
and an integral identity can be applied to the other fraction if you're allowed to use it
(or use x = tan(u) for that part)
ooh okay
i'll try that out
thanks
wait there isn't any (x^6 + 1) though
it's x^6 - 1 in the numerator of the question
i'm sorry if i'm sounding daft i'm half sleepy rn 😭
ah right
@raven spade Has your question been resolved?
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could I have a hint?
I think the last bit is wrong
maybe use something similar to the sandwhich theorm ?
or a trig substitution?
just a hint please
write $(1+a)^{n+1}=(1+a)(1+a)^{n}$
quickdoom
mhm
nothing, was just jotting down my thoughts
ohk
could I use a sub for $a\in [-1,0)$
ƒ(Why am. I here)=I don't Know
like $a =cos(2u)$
ƒ(Why am. I here)=I don't Know
There is no need of a sub, if you continue with this
You already know something about (1+a)^n...
it's more than $na+1$
ƒ(Why am. I here)=I don't Know
and so you can conclude something about (1+a)*(1+a)^n
correct
so what can you conclude about (1+a) * (1+a)^n?
(which is equivalent to (1+a)^(n+1))
it's more than $(1+a)(1+na)$
Usually with inductipn proofs you xan just follow the algebra
Wait are you sure about that?
oh there is just one mistake
right
okay so now you have this
expand and see what you get
$(1+a)(1+(n+1)a)$
ƒ(Why am. I here)=I don't Know
What js it?
this was correct
That is correct though
quickdoom
texsp fail
That term comes from just doing the algebra
Read the spoiler
(1+a)^3 = (1+a)^2 + a(1+a)?
Yeah?
we can clearly see that its not true, just by comparing the degrees. Or am I missing something?
i think you applied the induction hypothesis halfway there
Okay anyway, this was correct
now you can just expand that
ok,, so that gives me $1+na+a+na^2$
ƒ(Why am. I here)=I don't Know
okay, good
now you need that to be greater than (or equal to) 1 + (n+1)a
so think about how would you verify that
The line after the equality was a typo, here. I forgot to put a ^n on the second term
@sharp smelt Any progress? You are not far
right
treat it like those inequations where you are solving for x
just manipulate it smh
I can cancel outt terms
indeed
so this gives me $na^2 \geq0$
ƒ(Why am. I here)=I don't Know
which is when both are positive or negative
n>0
correct
a^2, not a
so this is always true
ok, let me try
$(1+a)(1+a)^n \geq (1+a)(1+an) \implies 1+na+a+na^2\geq na+a \implies na^2>0$
ƒ(Why am. I here)=I don't Know
Write = instead of =>
And, that series of implications doesnt lead us to what we want
it does, doesn't it?
We want to show that (1+a)^{n+1} \geq 1+(n+1)a
yes
the thought process behind that was correct, but now you just need to transform it to a proof
which should ideally look like this:
(1+a)^(n+1) >= ... >= ... >= ... >= 1 + (n+1)a
wait, what
the part where I told you to "solve" the inequation 1 + na + a + na^2 >= 1 + (n+1)a was mainly supposed to guide you towards the right manipulation
It is, but its not that elegant
the proof wouldnt be that readable
You already had (1+a)^(n+1) = (1+a) * (1+a)^n >= (1+a) * (1 + na) = 1 + a + na + na^2
now you just need to continue this and reach >= 1 + (n+1)a
Which term was the only one that didnt cancel when you did the manipulation?
uh
one minute
I'm lost sorry, I'll try this again tomorrow
is that fine?
@autumn fossil
ok
(1+a)^(n+1) = (1+a) * (1+a)^n >= (1+a) * (1 + na) = 1 + a + na + na^2 >= 1 + a + na = 1 + a(n+1)
and done
the key observaton was that most of the terms cancel, except for na^2
so we needed to remove that one
yeah, makes sense
and then its equal
,align[2\textwidth] (1 + a)^{n + 1} & = (1 + a)\2b{(1 + a)^n} \ & \ge (1 + a)\2b{(1 + na)} \ & = 1+ a + na + \2o{na^2} \ & \2o{\ge} 1 + a + na \ & = 1 + (n + 1)a
yeah you can go
sure
the non tex'd math was just making my eyes bleed 
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$$\text{Prove that} \frac{\int_0^{\frac{\pi}{2}}\log(\sin x)dx}{\int_{-\frac{\pi}{4}}^{\frac{\pi}{4}}\log(\sin x+\cos x)dx}=2$$
ugh that looks horrible
kheerii
sure I guess that kinda works
how I did this was write the bottom integral as $I_2=\int_{-\frac{\pi}{4}}^{\frac{\pi}{4}}\log\left(\sqrt{2}\sin\left(x+\frac{\pi}{4}\right)\right)dx=\frac{\pi}{4}\log 2+\int_0^{\frac{\pi}{2}}\log(\sin x)dx =\frac{\pi}{4}\log 2+I_1$
kheerii
From here, I solved for $I_1$ to get $I_1=-\frac{\pi}{2}\log 2$ which gives us the result combined with the other equation we got, $I_2=\frac{\pi}{4}\log 2+I_1$
kheerii
can anyone think of a way to solve this without explicitly solving for I_1?
what's that
for the bottom integral sub x --> -x and add it back to itself
ohh cos2x
you get cos 2x inside the log, then sub 2x
gotcha
yes
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How would you slolve this?
use the binomial theorem to expand (1+2/3)^-4
nvm.
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first convert it into a improper fraction
.reopen
✅
so 5/3
yeah. now solve
oh 3/5
That’d be if it were -1 not -4
yeah
3/5 ^4?
yup
ty
yw
.close
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,w 0.8^4
.6
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pls help is this solution correct?
Looks good
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How does one solve
$$4x^3+30x^2+66x+40 = 0$$
I got this as one of the last steps in the assignment, and I don't know how to continue from here. The answers in my book didn't really help me as they fastforwarded straight to the answer.
ReaMart
as far as I know this is a cubic/third degree equation. This is what the answer says:
there technically is an explicit cubic formula but that's kind of overkill
if you can find a single solution you can reduce it to a quadratic
hmm yes
rational root theorem helps you check for any rational roots here
which is always a good way to quickly find a root to reduce this
btw the function that is equal to 0 is called f(x)
and my book says
$$f(x) = 0 \text{ gives } x=-1 \vee x=-2\frac{1}{2} \vee x=-4$$
ReaMart
so is the problem coming up with those solutions?
yeah
do you know what rational root theorem is?
let me translate it real quick
okay
no I don't know it
if you have a polynomial with integer coefficients
then there's a finite possible set of rational roots
of that polynomail
and you can find out all possible candidates for the rational roots using this theorem
take all possible factors of the constant term and divide them by all possible factors of the coefficient of the term of highest degree
so for example, you can firstly rewrite your equation as 2x^3 + 15x^2 + 33x + 20 = 0
yeah
if you divide by 2 again you no longer ahve integer coefficents