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Let $\alpha$ be a root of $2x^2+3x+4=0$. Then find the possible values of $2{\alpha}^5+4{\alpha}^4+7{\alpha}^3+8{\alpha}^2+9\alpha+3$
deltaG
i want to know if my solution is correct, posting it in a while
nah bro trust me after looking at the solution youll kiss it
polynomial division? lol
since $\alpha$ satisfies the quadratic equation, $2{\alpha}^2+3\alpha+4=0$.\
using long division,
$2{\alpha}^5+4{\alpha}^4+7{\alpha}^3+8{\alpha}^2+9\alpha+3 = (2{\alpha}^2+3\alpha+4=0$)({\alpha}^3+{\alpha}^2\frac{1}{2}+{\alpha}\frac{15}{8}) + \frac{3}{8}\alpha -\frac{9}{2}$\
$\frac{3}{8}\alpha -\frac{9}{2}$ is the reduced version of that 5 degree polynomial and $\alpha = \frac{-3+- \iota\sqrt{23}}{4}$
and then i just put this value of alpha in that linear poly
deltaG
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so, then?
then i get the value
but my question is
why is this allowed? considering dividing by zero is illegal
yeah
Because you're dividing a polynomial by another polynomial
Can I ask a question
you're not dividing the numbers you get when you plug in something into that polynomial
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Ight sorry
ohh
makes sense
It's actually very nice because now the only thing you care about is the remainder (since the divisor evaluates to 0 when you plug in your root)
true, my mind was blown when i saw our math teacher do it
But it's not like dividing by the polynomial 0 which would be not so good
0/0 is not undefined, it is indeterminate
it's not illegal in legal sense as well
but how do we know that the numerator is also zero
alpha isnt a root of the above polynomial
This is a limit thing only
sorry, i didnt understand what you said here
does it now
0/0 is undefined, calling it indeterminate really only makes sense if you're a precalc/calc 1 student
and also it must be approaching to zero, right?
not really, no
Well there's the polynomial that's always equal to 0, called the zero polynomial, and you can't divide by that
isnt $2{\alpha}^2+3\alpha+4$ always zero?
deltaG
You need to think of polynomials as objects in their own right
That can be added subtracted multiplied divided without plugging specific values in
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Np
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How do we find the minimum value for this
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put it in and check if all of the equations are correct
🙃
.
maybe try to use a matrix
nah i have to use algebra
ok thats fine
so i get a+d=1?
and subtracting eq 3 from eq 4 gives me b-c=1?
@outer pilot (sorry for ping but i need hlep)
youll always get - if you are subtracting equations
lol dumb me forgot
if you sum them you can get +
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Not sure where I did wrongly prob the multiplacion part but I'm not sure how to simplify that
Ans was 0.1 if I'm not wrong
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@dry ore Has your question been resolved?
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have you had matrices?
they just said basic algebra
you dont even need matrices for this, just solve the system on your own
yes
or substituing
i tried a lot
did you now
cant find a solution
\begin{align*}&a+b+c=7\-(&b+c+d=6)\end{align*}
whats done here?
Flappie
what happens if you subtract the bottom equation from the top one
the easiest way to do this problem is to start by adding all four equations
hmm i didnt try that
wouldnt that make it long and complicated?
7 - a + d = 6
d = a - 1
c + a -1 + a = 8
c = 10 - 2a
a - 1 + a + b = 8
b = 9 - 2a
a -1 + 9 - 2a + 10 -2a = 6
3a = 12
a = 4
d = 3
c = 2
b = 1
messy way of doing it
its super simple
substitution is the brute force, but simple way to do it
i literally did it on a chat 
the numbers are wayyy too easy not to subsitute this away
this is your solution @craggy yew
ohhh
this is not a good solution
i feel so dumb
are you going to try this
is there a easier way to do the same?
i have been telling you for 5 min
bro the solution i gave him is like 10 lines 
and it's messy
3a+3b+3c+3d=30
but there is no way someone who only knows basic algebra is going to think of your solution
now divide by 3
then a + b + c + d = 10
cute
if a + b + c = 7
and a + b + c + d = 10
find d
ah
that is very clever
this is standard way of doing such problem
is it really
which is why i say substitution is messy / not good
where was my teacher 
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what am i supposed to do in the question
add a+b,b+c and c+d first I think
no like
what is meant by computing the greatest possible value
am i supposed to find the answer in algebraic form?
or is there a number u get from cancellation?
of that I'm unsure
adding all three equations and cancelling gave me 2b = -c
but isnt that wrong?
why would it be wrong?
because b is supposed to be a positive integer
yes
b is an integer, nothing is said about c
and c can be negative
a has to be negative
sorry i got confused
this is a good question, it's normal to be confused, don't insult yourself like that
arguable
how do i use 2b=-c to solve
you can then express a in terms of c too
right?
and then d in terms of c too
does that make any sense?
@craggy yew
@craggy yew Has your question been resolved?
hmm
how
ƒ(Why am. I here)=I don't know
so a is ?
.
-3b
-b?
-5b
good
and b is a positive integer
I'm taking that to include 0
so then the answer is?
?
do the positive integers include 0?
whats that supposed to mean
ohhh
the sum is -5b , right?
yes
?
infinity?
(sorry battery died so went afk for a while)
the book doesnt have solutions
let me look it up
and i cant find the arml 1990 solutions
ok
why should b be as small as possible?
does that make any sense
no
which sum?
a+b+c+d=-5b, yes?
yes
and b >1?
why cant it be 1?
I meant $b\geq 1$
ƒ(Why am. I here)=I don't know
now?
yes
yes
so now does it make sense
is -5 bigger than -10?
ys
wait what is meant by maximising?
here just finding its maximum value
well since b can be any value
greater than or equal to 1
shouldnt it be multiplied by -infinity?
negative infinity?
im confused so can u reveal the ans?
b=1
why
we want to get a value for -5b that's as big as possible right
and $b\in [1, \infty) \in \Z$
ƒ(Why am. I here)=I don't know
yes
so what value of b would you chose
infinity
ƒ(Why am. I here)=I don't know
because its a big number
ohhh
ok, is $-5 \cdot 1$ bigger than $-\infty$?
ƒ(Why am. I here)=I don't know
does the answer make sense now?
i see why its 1 now
cool

thanks for helping me so much!
no problem, this was a fun question
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✅
(sorry for ping) @twilit field one last question
sure
how did u get the answer of -5 by -5b?
b=1
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how do i solve this integral
this would be my approach dunno if it is correct
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can someone help me with this
i need help with g
and h and i
what i have so far
it seems i’m wrong for concave up and down
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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
show where you are stuck?
I’m not sure where to move what
well start by clearing the denominator on the RHS
Like I tried moving the 3n-2 over to the left but didn’t know what to do next
then rearrange so you have all the terms containing N on one side
and everything else on the other
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!original
Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.
!original
Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.
Ye but my teacher did it without expanding and when I did I still got the wrong answer but was close
you can also divide
Divide pi r
so then what do you get
A/pi r= r-x
now, isolate x
Was it
After this step I mean
Don’t u divide -1
if you dont tell me what you did
then what do you get?
R-(A/pi r)=x
Maybe the textbook got it wrong
what does the textbook say
it's the same
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Please help with the 7th one
Yes n then
+x-x cancel out
Okay
(1-x)(1+x)=1-x^2
Okay
did you get it now?
Yesss
we just got 1-x^2 from multiplying 1-x and 1+x
Okay
and 1+x^2 is already there in numerator
Okay
so now multiply them
Yayayayya
which gives 1-x^8
(1-x^8)(1+x^8)=1-x^16
Which will give 1-x^16
(1-x^16)(1+x^16)=1-x^32
np
now close the channel fr
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(Sorry for interrupting but, what grade are you in? Or are you in collage?)
9th
Just started
Why tho?
Oh ik that's easy but my head is messed up so I wasn't able to do
(We cant talk here after you closed the channel, dms if u wish)
Nah it's okay
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Question d is c2=a-b2 corrrect
Squared btw
Does b squared plus c squared equal (b+c) squared
you want to make a the subject
Yes
you need help with d)?
Yes
ok
It says square first
@storm09 can you sovle i plase 🛳️
?
get your own channel
not this guy again 💀
he has 2 of his own
on the right track but next subtract b^2 from both sides
Subtract?
Ye
no no no
Ye that’s what I thought
$(b+c)^2 = b^2 + c^2 + 2bc \neq b^2 + c^2$
this is GIVEN that 2bc is not equal to 0
ren
So I get a equals b^2+c^2
fr
the question here is different from what you wrote
c=sqrt(a)-b
add b on both sides
b+c=sqrt(a)
The book wants me to square first
So the book telling me one thing but gets the answer differently
yes lmao
Where u get 2broota
Root a
Just to c
O u have to square the whole side
Like (sqrt a-b)^2
yes
np
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find d to maximise theta
the calc solution is horrendous algebra,
a geometric sol would be greatly appreciated
@acoustic sparrow Has your question been resolved?
here is one way: try and look at which theta works
hint: if theta works, what would the circumcircle passing through the triangle with angle theta and length 5.6 look like?
analyse for which theta does there exists a right triangle looking like the graph
no, it more like asking the question: does theta=80 degrees work? how about 70 degrees
if you can distinguish which theta works and which theta doesn't, then you can just find the maximum of theta
and the hint is drawing the circumcircle of the triangle with angle theta
note that the angle theta uniquely defines a circle passing through BC
why does it?
all the points that forms angle of value theta with BC lies on the circle
?????
given B,C the set of points {D: angle BDC=theta} will look like a circle
this is because if D, E are on the same circle as B,C then angle BDC=angle BEC
and if angle BDC=theta, then the circumcircle of BDC will have center O such that angle BOC=2theta
you can prove that there is only 2 possible O that satisfies this
may I ask what is your background in geometry?
i get you can define a circle with 3 points
but i cant understand what youre writting
Can you prove the following:
given two points B,C on the plane, show that the set of points {D: angle BDC=theta} is the union of two circular arcs?
no
try to prove it, it will help getting an understanding of the relation between circle and angle
do you understand the statement though?
no
take 32 degree for example
I am saying all the points that forms a 32 degree angle lies on two circular arcs:
as outlined by the red line
i am saying all the points that forms 32.019922285598 degrees with BC lies on those arcs
yes
now do you understand the statment?
if so can you attempt to prove it?
I can't give a solution until you understand those things (as these things are needed in the solution)
but you can show that the circumcircle must be tangent to the d there
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so im doing limits
and i can't go any further in it
i did p=f(x)-mx
but can't go further
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@heavy falcon Has your question been resolved?
<@&286206848099549185>
In this kind of questions they ask for an enclosed area like shown here, the keyword is that the area is bounded by C, the line d and x=2. Origin could be said to be a boundary to the area, that is to say, the cyan and yellow areas are separate.
but it wasnt specified that the area is taken to be bounded by x=0
what matters is that it is bounded by (C),(d) and x=2
also how do i know that 2 is the upper bound not the lower one for for example
shouldnt the curve be draw from x=0 to indicate that at least
to indicate this i mean
the thing is I see yellow and cyan areas as different bounded regions, and they ask area of a specific bounded region. By the topological definition of boundary, it being the points of closure (those that limit the region) and are not inside the region itself, the yellow and cyan areas would be strictly speaking different regions.
although what i am considering to be one region still satisfies all the named conditions no
because the area from -inf to 2 is bounded by (C) and (d)
i dont see how it isnt
but the cyan area is not also bounded by x = 2
but the area of cyan + yellow
is
i am finding area of yellow+cyan
which is bounded by x=2
and also bounded by (C) and (d)
the yellow region alone is also bounded by (C),(d) and x=2
but one cant determine which is the one to take if it is not specified am i wrong
and since the only boundary for x is 2
then we will have to consider it unbounded by any line of equation x=a from the other side right?
yes, apparently you are right, here's one example where a single point is not enough to limit a region. Need to check again what a region is I guess.
yes here the region is specified to be between 0 and pi
and pi isnt an intersection point that lets the are be enclosed by a "closed" shape
same thing for 0
and this is the same as the one that you split into 2
so what to do now
What's remarkable at least is that they make a distinction between the regions R1 and R2 and also they say R is a region not a bounded region. In any case, I don't think I can help much more, since I am not that knowledgeable about these concepts.
yes they split them at the intersection point
because one of them is below the other before the intersection
and this changes after the intersection
you are finding the area so you will have to integrate the abs value of the difference
thats why
and it isnt necessary to mention if it is bounded or not the boundaries are already clear
tysm
and sorry if i wasted your time
<@&286206848099549185>
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im stuck on i, i thought that i needed a domain for the range?
so just any number works?
when x belongs to R, range of F(x) is R
for a and b
part
for i part of the q
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how did we get the underlined equation
whos person A
Al
ok, what about Bob
10 ft/s
8 ft/s
shouldn't it be 16?
i might be wrong
why tho
after some time bob will be ahead and al will be in the middle
good
and we have to find the distance between al at that point and the beginning of the walkway
i think
the time is measured from the time the first person steps on the belt
so one person's coordinates are $8(s-4)$
ƒ(Why am. I here)=I don't Know
whys it 8(s-4)
they step on the belt 4s later
isnt that the distance?
yes
but like
bob's overtaking and al going in the middle will take a lot of time right?
why is it only 4 seconds
oh wait is this supposed to be its original position when cy stands on the walkway?
so why is the time s-4
cy starts walking only after 4 s
wait what time is s
when Al is half way between cy and bob
at what position are the people in s-4
I don't follow
why is 4 subtracted from s
because cy starts moving 4 seconds later
yes but why do u need to do that
because you're measuring time with respect to the person who started first
what happens during s-4
that's when Al is inbetween
what happens during s
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I don't follow the second step here
from let k be the largest element ...
like how are we sure dividing by a common factor will give is $v_k$
ƒ(Why am. I here)=I don't Know
kk thanks
what do you mean?
a_1v_1 + ... + a_kv_k + ... + a_mv_m = 0, so we rearrange for v_k
such a k must exist cause v1,...,vm is LD
so Axler is just choosing the largest k for this
ah
I thought we couldn't assume this statement to be true
sorry
thanks

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✅
wait
bro didn't even give us a chance to help 😭
now u can tho
do you know the value of the gaussian integral?
e^(-x^2)?
if you need to derive that from scratch it's doable but it's a pretty famous result
you can just make a u-substitution with u = x / sqrt2 to turn this into half of the gaussian integral
is there a specific technique they wanted you to use?
polar coordonate system
The gaussian integral - integrating e^(-x^2) over all numbers, is an extremely important integral in probability, statistics, and many other fields. However, it is challenging to solve using elementary methods from single variable calculus. In this video we will see how we can convert it to multivariable calculus and then use tricks from multiva...
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what rules are used here? im tryna mark my hw but the answers skip steps or im struglling to follow along with whats happening😭
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ty
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find all $x \in \mathbb{R}$ such that the series converges, $\$indicate for which values the convergence is absolute $\$and for which values the convergence is conditional $\\ \sum_{n = 1}^{\infty} \frac{x^n}{n^3}$
938c2cc0dcc05f2b68c4287040cfcf71
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
1
do you know what the interval of convergence is?
the interval for which the series converges
do you know how to find the interval of convergence using the ratio test?
,, \lim_{n \to \infty} \left| \frac{\frac{x^{n+1}}{(n+1)^3}}{\frac{x^n}{n^3}} \right| < 1
938c2cc0dcc05f2b68c4287040cfcf71
this?
yes
now let’s try to simplify this
sure
,, \lim_{n \to \infty} \left| \frac{n^3(x^{n+1})}{x^n(n+1)^3}\right| < 1 \ \lim_{n \to \infty} \left| \frac{n^3 \cdot x^{n} \cdot x}{x^n(n+1)^3}\right| < 1
I did nothing fancy
let me simplify
938c2cc0dcc05f2b68c4287040cfcf71
okay
,, \lim_{n \to \infty} \left| \frac{n^3(x^{n+1})}{x^n(n+1)^3}\right| < 1 \ \lim_{n \to \infty} \left| \frac{n^3 \cdot x^n \cdot x}{x^n(n+1)^3}\right| < 1 \ |x| \cdot \lim_{n \to \infty} \left| \frac{n^3}{(n+1)^3}\right| < 1 \ |x| \cdot \lim_{n \to \infty} \left|\ \frac{n}{n+1}\right|^3 < 1
lmao
we can pull x out of limit
yep
we need to expand (n+1)³
or
n^3/(n+1)^3=(n/n+1)^3
well what does n\n+1 approach
if we factor by n and cancel both n from numerator and denominator the limit is approaching 1/1
you can’t factor by n
dont forget that |x|
but you can do lhopital
938c2cc0dcc05f2b68c4287040cfcf71
so -1 < x < 1
yep
$x \in (-1, 1)$
938c2cc0dcc05f2b68c4287040cfcf71
but about the convergence being conditinal convergence or absolute convergence?
which values of x absolutely converges which values conditionally converge
you used the ratio test, right?
yes we used ratio test
what does the ratio test say when its conclusive
< 1 means its absolutely convergent
absolute convergence is stronger than conditional convergence
if $\sum |a_n|$ converges, then $\sum a_n$ also converges
Flappie
if $\sum |a_n|$ doesn't converge, then you cannot say anything about $\sum a_n$
Flappie
with the ratio test, you conclude that $\sum |a_n|$ converges
Flappie
thus, it is absolutely convergent
yes there is no x in R such that it conditionally converges
because |a_n| converges
anyways thank you
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My teacher gave us problem (b) and said that if we wanted to, we could use the “difference of squares formula” to solve it. I used that formula in the second picture because it’s much quicker.
However I wanted to try figuring it out without the formula in the first picture, did I do it correctly?
@severe glade Has your question been resolved?
<@&286206848099549185>
looks right to me
in general though, i agree with your teacher
Okay thank you, is the difference of squares considered a formula?
stick with the difference of squares formula, it will be much quicker
Or a property
formula
properties are things objects have (ie integers are either even or odd)
the same way we consider the quadratic formula a formula and not a property
Also is there a list of formulas I should I know? Cause tbh I feel like every other class my teacher mentions a “formula shortcut” that we can use to figure out but I always feel like I don’t rememebr it when she brings it up
what class are you taking?
Like for example when she mentioned this one in class I didn’t remember it at all
algebra 2?
i would say you should know the following
yes true
Sridhar Acharya Formula
besides those i dont think there are very many formulas i needed to use during my pre calc class
same thing ¯_(ツ)_/¯
Thanks I appreciate it.
Is there not a list of formulas similar to how there’s a list of “law of exponent” and “radicals rules”?
yup
For exponents my teacher gave me a list of exponent rules to remember
And radicals
But I was curious if there was a list for formulas I should know
there's also completeing the squares method
So I can just review them
im not sure if theres a generalized one
you're probably better off going to ask your teacher
to see which formulas they would want you to know for their class in specific
yeah ig there's a good ig page for generalised formulas
b/c obv my advice is personalized to the course i took
its called math vibes or smtg
it gives good charts with tricks sometimes to remember those formulas
Okay gotcha.
Jw in the first picture I sent
Is that method I used called factoring?
Where I broke it down
Ohhhh
factoring is when u make the stuff smaller
u did at last by applying identity of (a-b)^2
this complete method is called simplification
Got it thank you both for ur help I appreciate it
Always 
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the numerator should be a polynomial of 1 degree less than the denominator
@white loom Has your question been resolved?
just C, if you have the sum of two unknown constants you can combine them into a single unknown constant
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I have to calculate the partial derivative of a function at a point, using the definition
!original
Please show the original problem, exactly as it was stated to you, with the entire original context. A picture or screenshot is best. If the original problem is not in English, then post it anyway! The additional context might still be helpful. Do your best to provide a translation.
This is the original function
The task is to: Using the definition, calculate the partial derivatives of the function ( f ) at the point ( P_0 ).
john3515
[ \frac{\partial f}{\partial x}(x_0, y_0, \ldots) = \lim_{\Delta x \to 0} \frac{f(x_0 + \Delta x, y_0, \ldots) - f(x_0, y_0, \ldots)}{\Delta x} ]
john3515
this is with respect to x
have you tried plugging in f and seeing what happens?
didn't I do it in the picture I sent before?
how do I proceed
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For question D (blue problem) are both my answers technically correct?
@severe glade Has your question been resolved?
<@&286206848099549185>
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Say we have a simple circuit with a battery,bulb and a resistor
yes?
the internal resistance of the battery is 0?
Yes
Normally batteries are defined by that V
So if it's a 3V battery, that will read 3V
But didn't we already split the voltage across the bulb and the resistor?
use KVL
Kirchoffs what?
Voltage law
That exists?
yes
I know only junction law and loop law
It's probably loop law
"Voltage drops = Voltage gains around any loop"
It's commonly referred to as KVL
If that battery adds 3 volts, then the lamp and resistor are going to burn those 3 volts
Oh
Say buld uses up 2 volt and the resistor uses 1
V3 reading would be 3 or 0?
It's 3
But then wouldn't the potential of the whole circuit be equal to 6?
remember the battery supplies voltage and the bulb and resistor use that voltage