#help-38
1 messages · Page 59 of 1
how
$(2^x)^2 + 3 \cdot 2^x + 4 = 0$
south
becomes $u^2 + 3 \cdot u + 4 = 0$
south
what is u
u = 2^x
yes
Inuji
nah it's $u^2+3u+4 = 0$
south
shit this one isn't factorisable sorry
oh
how do u factor something unfactoriable
???W
is there no other way
i really hate formulas
cuz u have to memorize so long
nah
don't worry your problems won't be this nasty
can u give more
do you have any textbooks?
do u need formula\
for this
no
you just need to use the prime factorisation
you want the powers of 2 and 5 from 30^9
cause 400,000 is only made up of powers of 2 and 5
so that gives 10^9 = 2^9 * 5^9
and 400,000 = 4 * 100,000 = 2^2 * 2^5 * 5^5 = 2^7 * 5^5
how
what is the 30^9 for?
im actually a competitor for math olympiad, idk how i qualified
😆
and what to do next?
oh wait you do need the 3^9
so 30^9 = 10^9 * 3^9
so 2^9* 5^9 * 3^9
yeah so if you have 2^7 * 5^5 that will work
if you have 2^7 * 5^5 * 3 that will work
if you have 2^7 * 5^6 that will also work
as long as you're under 30^9 = 2^9 * 5^9 * 3^9
how many ways are there to choose the power of 2
such that it's between 7 and 9?
ii dont seem to understand
$oh wait you do need the 3^9
so 30^9 = 10^9 * 3^9
so 2^9* 5^9 * 3^9
yeah so if you have 2^7 * 5^5 that will work
if you have 2^7 * 5^5 * 3 that will work
if you have 2^7 * 5^6 that will also work
as long as you're under 30^9 = 2^9 * 5^9 * 3^9$
Inuji
let's try with smaller numbers
like 300 and 10 for example
$cause (2^2 * 5)/(2 * 5) = 2$
Inuji
yes
so we just need to choose a power that is 2^1 or greater
and a power of 5^1 or greater
as it will divide evenly into 10
so $300 = 3 * 100 = 3 * 2^2 * 5^2 right$
Inuji
yeah
where did the 5^2 go
so it disappear?
no
yes
20 and 50 are all multiples of 10
so if our prime factorisation has 2 * 5 or greater
it will also be a multiple of 10
what does greater mean
more
examples
2 * 5 * 0.5 is 5 tho
we're not counting fractions
ok
then
how do we determine
its less than 300
right, so for the powers of 2
we have 2^2 in 300
and 2^1 in 10
that means our power of 2 can either be 1 or 2
can u show it in numerical form
so like 2^2 * 5 = 20, a multiple of 10
2^1 * 5 = 10, a multiple of 10
2^2 * 3 * 5 = 60, a multiple of 10
but we can't have 2^3 * 5 = 40
that's a multiple of 10
but it doesn't divide evenly into 300
cause 300 = 3 * 2^2 * 5^2
only has a power of 2^2
in other words, the maximum power of 2 that can divide evenly into 300
is 2^2 = 4
so 2^3 = 8 or any higher won't work
answer is 8??
no
so there are only two choices for our power of 2
2^1 or 2^2
nah I would recommend you work on your fundamentals first
which
specifically prime factorisation
and combinatorics
cause this is the example with 300 and 10
the original question has much larger numbers
you don't know combinatorics right
and that ok
no
like if u tell me
what is the prime factor of 100
i know
yeah but there's no point then
but idk how to use
so you couldn't find a prime factorisation yourself?
like say 72
yep
12(3)(2)
yeah
(3)(2)(2)(3)(2)
Inuji
yeah nearly there
$2^3 \cdot 3^2$
south
yeah so you can do it
cause the olympiad problem is testing skills way ahead of where you are now
yeah but idk how tf i got qualified to join
idk
right??
yeah that's really strange
i only joined cuz the teacher told us there were extra grade for joining
i didnt expect to get in
lol
so whats the answer?
you won't understand the answer to the original problem
i wont understand it anyway
yeah so 300 = 3 * 2^2 * 5^2
so go for the smaller
and 10 = 2 * 5
so (2 - 1 + 1) = 2 choices for the 2
(2 - 1 + 1) = 2 choices for the 5
and (1 - 0 + 1) = 2 choices for the 3
so 2 * 2 * 2 = 8
if you count there are 8
nah but only 8 are divisible by 10
10, 20, 30, 50, 60, 100, 150, 300
where did u get -1 from
there are 10 numbers between 1 and 10
that's the same as 10 - 1 + 1 = 10
so we're finding how many numbers there are between 1 and 2
2?
yes
btw you can get 18 divisors in total
you can choose 3^0 or 3^1
2^0, 2^1, 2^2
and 5^0, 5^1, 5^2
so 2 * 3 * 3 = 18 choices in total
18 divisors
;-;
yeah that's the principle behind it
yes but only those with more complex
like rational function?
depends
can you give me an example, maybe that can help
alr
like
quadratic equations
and the letter e
@wraith garden Has your question been resolved?
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https://gyazo.com/0615e041b5aa174c3486a0d665d153ed?token=2977a434977dc6971284b2c51a5f7df0 hello could anyone help with a)? i have no clue how to approach it
@jaunty topaz Has your question been resolved?
<@&286206848099549185>
do i just multiple each y value by its corresponding joint probability?
and add them togethe
@jaunty topaz Has your question been resolved?
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I don’t remember what gets that summation be negative and then positive
I see that it goes to 10, being squared, though I don’t see how to get the minus and addition in it
What is (-1)^2 and (-1)^3 ?
1 and -1
Exactly, -1 changes depending whether the power is odd or even.
Still, it doesn't matter how the sequence change, put a - sign infront, it still changes.
Hmhm
See how the sequence appear with $-\frac{1}{n^2}$
Bot is down
Oh
It be continuous negative fractions
Ooo
-1^n/n^2
Nah
-1^n/-n^2
Yh it is that
Thank u
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Basically solving this term (sequences and series)
rearrange the terms
Check the answer
Thank you 
How
your answer is negative
Yes
what do you mean?
The 8,64,512
yes
Has a negative sign before it
yes
So the sum of GP also has a negative sign before it
yes
So where am I wrong
try it this way
Man this is confusing 😭
(6+48+384...) - (8+64+512...)
I will try using this
two geometric series
let me see
This is the given answer
your brackets are different
from the given
let me try it that way hold on
I don't get the given answer either
$\frac{2(8^{36} -1)}{7} + \frac{4(8^{36}-1)}{7} - \frac{8(8^{18}-1)}{7}$
WOWWA
aren't these the correct exponents?
there aren't 30 negative terms in the sequence.
There are 90 terms so 30 terms for each series
Since -8 is the 3rd term the 90th term will be from the -8 series
Hence the remaining will also be 30 and 30
How?
I mean
look at the sequence
for every 4 positive terms
there's 1 negative term
oh what ur right hold on I'm tripping
128,256,-512
lol it's okay
wow that was big mind blunder
We will get there together
Happens
ok wait with this newfound knowledge
I just don't understand how he just adds these up and brings it to 14/7 [~]
No..?
yes
So,( 2 + 4 - 8)
Nah it's 14/7
yes I see now
Let me complete the lec and check in again
Same thing
not same thing doe
He probably forgot to add the bracket
ye probs
Does that sometimes
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!status
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okay, can you do g(5)?
uhh no?
why not?
Just substitute x=5 in g(x)
i know but what does the small 3 do
g(x) = 3 i think
well not quite, g(5) = 3
it's only true when x=5, not when x is anything
okay, so now we have g(5)=3 - what's f(3)
so x is 5?
we have set x=5 in g(x) and gotten 3.
and now we want to calculate f(x) where x=g(5), which means when x=3.
f(3) is 5?
looks like it, yeah
so what's f(g(5))
so its 5?
yes
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For differentiation, does dx^2 equal to 2xdx? If yes, what is the logic and the meaning of d?
Okay so afaik, d/dx means derivative
So if dx^2/dx = 2x
Then I can say that dx^2 =2xdx
Seems correct but what is the logic here? What do d and dx indicate and why am I allowed to multiply and divide with them as if they are some numbers
@stone garnet Has your question been resolved?
they "are" numbers
but they are very small so we represent them by "d" or delta
d/dx should be looked at more as an operation, that behaves like a fraction, not an actual fraction
(this allows for the chain rule, for example)
There is a very popular question about this on MSE
See the first answer there
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Determine a point and a direction vector of each of the lines that have the following equations:
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How can you tell which function is represented in a graph?!!
Mostly it's just guessing from experience
wdym?!!
If you were given a graph and asked what function is presented on the graph, you would need to guess
oh ok!
How do you find a domain if it does not touch the x- intercept in the graph?!
I suppose you mean the x-axis
Yeah I do, sorry about that!! xd
Not touching the x-axis is irrelevant to the domain though, you might want to rephrase the question
I guess my brain got comjumbled with information!
How do I find the domain of a parabola?
Usually parabolas are defined on the entire set of real numbers
So, if you are given a graph with no points missing, you should be safe to assume that the domain is R
But if any points are missing, exclude their x-coordinates from R
Depends on the context I guess, how does the graph look?
The line is l-shaped, meaning it is an Exponential graph!!
The function is g(x)=2(0.5) to the power of x.
I guess what they are expecting you to say is that the graph approaches the x-axis (or, simply, that the x-axis is its asymptote)
It is asking which has the same end behavior for large, positive values of x!!
Yeah, this should be it then
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Need help on question 12. Don’t know how to start
!status
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6. I have completed the problem and don't need help anymore. Thank you.
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1
Hi, can you crop number 12 and send it here?
ok
Appreciate it. 🙂
Let me solve it for you?
if i can just find out how to start i think i'll be able to do the rest
Ok
Equate 2x + 20 and 5x - 37
to find the value of x and plug in the value to find the measurement
but how do we know they are equivalent?
?
Ok hold on, wrong. I apologize
the paper in general is about the perpendicular bisector theorem (and its converse), and the angle bisector theorem (and its converse)
try to establish a relationship between traingles FIG and HIG
also do notice both are right-angled triangles
yeah
wait even though the paper is about this you can prove their congruence using HL (hypotenuse-leg) right?
Solve for x
well not exactly
so basically SSA does not mean congruent
but since the angle is 90 degree the other side has to be same
I did not learn HL at school..but yes this is a case of HL that you have mentioned
so i can say congruent because HL?
yep
ok one last question about this specific problem
yes tell me
how do i know that 2x+20 is equal to 5x-37 and not the other angle in IGH (besides 5x-37 and the right angle)
that is based on ordering
we say triangle FGI is congruent to HGI
oh yeah
but we can't say triangle FGI is congruent to GIH or IGH
so f=h, g=g, and i=i
this means angle FGI = angle HGI
angle FIG = angle HIG
angle GFI = angle GHI and similarly for the sides
no problem
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im sorry if this isnt the correct server to ask but
which the formula is a^3
its stated here, however that it is mm but the density is cm^3
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what is the dot product of 2 parallel vectors?
it's the absolute value of 1, right?
what do you think it should be?
the absolute value of the dot product hsould be 1, right?
and if they are not?
are you familiar with
$$a\cdot b = |a| |b|\cos(\theta)$$
Bungo
forgot about that. So if they're parallel, then cos(theta) is 1.
or -1
So the dot product of parallel vectors is the product of their magnitudes
but then take abs value, it's 1
so am i right in saying that if vectosr are parallel, the dot product is the product of their magnitudes
well you need to look at its abs value tho
the abs value of the dot product is the product of their magnitudes
right
the dot product itself is either + or - the product of their magnitudes
okay thank you so much
sure, gl
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Hey quick question, do RYA(reflection in y-axis) makes points for x-axis and RXA(reflection in y-axis) in y-axis when making a new points?
For example,
\begin{enumerate}
\item (f(x)=\frac{1}{2}(2)^{-x+4} -8)
\begin{itemize}
\item \textcolor{red}{VS by 2}
\item \textcolor{red}{RYA}
\item \textcolor{red}{HT 4 (\to)}
\item \textcolor{red}{VT 6 (\uparrow)}
\end{itemize}
\end{enumerate}
My new key points from the equation above makes new point for x as \
$\boxed{\textcolor{OrangeRed}{-x-4}}$ and for y $\boxed{\textcolor{Melon}{2y-8}}$
but why?
Akira (fumo)
I want to understand why RYA goes to x section instead of y
does this mean same thing goes for RXA but for y-axis?
I can show my paper to see what my teacher did im kinda confused
<@&286206848099549185>
I'm not sure I understand what you mean by "making points for x-axis". What about "new points"?
Are you describing f(x) in terms of translations and reflections? Or are you starting from f(x) and then saying that the point (x, y) is mapped to (-x-4 , 2y-8) after the transformations?
Sorry if this doesn't really makes sense since my English sucks but I'll try my best from what I want to understand. Let's say we're making a new table for g(x) by using the transformations for the function(key points). I'm asking why the negative goes to x part table when it's RYA in the f(x) instead of y part on the table and same thing for y but RXA
OK, so if I got this right, you're wondering why reflecting about the Y-axis changes the sign of x, and why reflecting about the X-axis changes the sign of y?
A point is mapped to it's mirror image with respect to the x axis. The same distance from it, but the other way.
Functions are just collections of points really, so a reflection about the x-asix applied to a function will change the sign of all y coordinates.
This is the other one, same distance to the y axis, but on the other side.
Oh alright I was thinking that, in page 2 where it says $f(x)=-2\left(\frac{1}{2} \right)^{x+4}+8$. When we write transformation in the equation it has RXA. So, the y-axis will be $-2y+8$. Same thing in page 3 where it says $f(x)=\frac{1}{2}(2)^{-x+4} -8$ it has RYA. So -x-4 right? Does this apply to every example? I know how transformations works in other but just getting confused about reflections
Akira (fumo)
But I think I got it now

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Could someone describe how this equation works?
@karmic solar Has your question been resolved?
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Can someone help me with this question
i got the big radius as 1-y^2
and small radius as 4
and i set up the integration but I'm not getting the right answer
As a first thought, you might want to explain the question a little more. We do not all have your context. I guess you are after a volume of something 3D? Not obvious what the x=4 has to do with the curve, without a lot of guessing.
oh yea
my bad lol
im trying to find the volume of the solid created by revolving the region bounded by the graphs
I’m assuming interior area here is between x=4 and x=5-y^2 and you need to find the solid if revolution using the ring method
So here what you want to do is find the intersecting points of both graphs to find the bounds of your integration. Since this is around the y-axis you want to find the area between curves down to the y-axis.
Your integral should look something like this
Where R is the exterior curve and r is the interior curve
@crisp rivet Has your question been resolved?
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I'm getting stuck here
are you proving a statement here?
I'm proving one side is equal to the other, yes
any luck?
workin on it
alright, because according to desmos
it's matching
wait
no it isn't
not matching
gotta check my algebra
nvm
it is
mistyped
lol
nvm I got it
the trick was
to factor out cos^2y
from the first two things
in ba+ab+c, I factored out b
Yeah I was kinda getting those steps
This was one of the trickier ones to do
If you solved it don't forget to close the channel #help-38 message
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I can’t get -2 as the answer no matter how hard I try
I know how to solve it but I just can’t get the answer I’m looking for
Show your work, and if possible, explain where you are stuck.
What did you try
Basically
I subtracted one equation from that side to get
(X+5) - (5-2x)
@wraith hinge Has your question been resolved?
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I understand you have to bring out the 10. I just don’t get what to do afterwards.
sub x = tan(theta)
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Hello! I’ve got three questions that I’m not sure how to start on. I really just need to be walked through the actual steps of completing them.
Thank you
To whoever helps me, we can start with the antidepressant question.
Hi
Hello
what is the problem with the first question?
I’m not sure how to find the inverse of the function.
So would my f(x)= -0.088x + 2.99 be written as:
y= 0.088x - 2.99
So it would be 0.088y instead?
yes, -0,088y that is
don't forget to solve for y
Yep 👍
alright 👍
well same thing
switch y and x's place and solve for y
@fading narwhal Has your question been resolved?
Okay cool, and the graph is symmetrical with respect to y = x I believe?
Yes
I have the scatter plot graphed
But I’m not sure how to find the function for it
I tried to use y1 ~ mx1 + b and got the regressions etc. for it, but I’m not sure that’s what I’m even supposed to do
well it states in question a that it's an exponential function
so that gives us some information, such as that the function in question must be of the form y = a^x + b
I’m not really sure what A and B are in this problem
We can solve for b by looking at the first value.
If we take 1955 as the 0 for this graph
we know that b must be 407,8
since a^0 = 1
we can solve for a by plugging in values
So right now we are at:
y = a^0 + 408.8
Close
I’m a little lost I think 😂
Why is it 407, 8? Is that an ordered pair?
the first value is 408,8 yes?
that is at x = 0 since we're saying that 1955 is the x coordinate of 0
if we put in x = 0 at the function we get 1
a^0 = 1
if we did not subtract 1 from the last part we'd have 409,8 which is not equal to the first y coordinate we have
Ohhh
Okay I’m on board now
Hahaha great XD
then we can fill in multiple values of x and y to get something that's close to a
I lied, maybe I’m not on board. Everything looks like word soup to me right now, sorry 😭
Okay hold on hold on
This is where I’m at
My class doesn’t have a textbook
Alright
you want to know 'a' right?
at least, a close enough value that fits with your table of values
I think I’m just trying to get the actual function equation itself
well you have everything, you just need a for the full function
I’m losing it a little bit, I’ve been doing math since ~6am this morning 😭
Hahaha no worries
just fill in the x and y values in THIS function and solve for a
with every x and y value
so first off fill in x = 10 and y = 835.5 and solve for a
Yes
and for y = 835,5
next x = 20 and 2306,5
Hold on gotta see if im correct first
Your commas are supposed to be decimals, right?
Oh I gotcha, no worries 👍
I was seeing them at ordered pairs at first, and that added to my confusion, sorry lol
haha no problem
I’m blanking right now. How do I solve for a
I’m embarrassed for asking 😭
I need to
Ah I gotcha lol
Hold on a sec
alright
So the exponential function is N = b g^T
with b as starting number and g the growing factor
and t is time
N = 0 408.8^t ?
N = 408,8 g^t
I understand your confusion this is hard :(
but I now know how to solve it
Forget Everything I told you
Okay lol
im checking if what i did was right lolol
All good : )
If this helps at all
On the example problem for this one
They say the answer is this
So our answer has to be in that same form
y = 337.906 (1.084^x)
yes exactly
y = b g^x
Alright I know it
Pick 2 points and divide the highest by the lowest
Yea that's fine
and then do root it the number of years apart
so for your point that's 35 years apart
so the 35th root of 12.25
1.07
it's more exact if you instantly put the fraction to the power of 1/35
1.074
so (10231/835,5)^1/35
Yesa
Correct
1,074
you can do it with more values to get a more exact a but this is basically it
so it's y = b 1,074^x
Okay so that’s one half
How do I solve for b
b = the value when x = 0
the text says that x = the number of years after 1955
so 1955 = (x = 0)
Okay I’m confused again. This is the example problem here:
Why is their’s not 409.1 ?
Most likely because this question says that the starting year is not 1957
but some year after that
Their starting year is 1957
I actually have no clue
it doesn't even work
I don't think that that equation is correct...
Okay just getting it back down here, this is the one we’re working on currently
well the answer to your question I THINK is: y = 408,8 (1,074)^x
yes devide the higher value with the lower value
and root it the difference in years
that's your growth factor
Yeah we’ve got that part
and your b SHOULD BE when x = 0
It’s just B that we need
Should we get another set of eyes on this in case there’s something we’re missing / not seeing?
The rules say we get one if we don’t get help in 15 minutes, but I’m not sure what to do in this situation
Oh nvm
I think the example question is wrong because it really just doesn't make any sense at all
x = 0 should be 409,1 but the formula says 444,23
which just isn't correct
so I understand your confusion XD
If it was just purely my college, then I’d think it was 100% wrong, but my professor is the one who helps us through the problems and this is what she got, and then the system itself said the answer was correct
So both my professor and college agree on it
But it sounds like it’s not even a possible answer
put in 0 for x in the example question
you won't get 409,1 right
I REALLY WANNA KNOW if im just crazy or if this question is wrong
It just gave me 444.23 back
444.23(1.076^0) = 444.23
Is that what you were asking?
Hahaha don't think so either
409.1
We’ll try it
maybe they want an approximation
If I press help me solve this, it runs through TI-84 instructions
Maybe I’ll try that with ours and see what we get?
Sure
I think they'll put in values for x and y to solve for the b value
For better approximation you can try more values but it's more work
Okay interesting development
The second example problem is also different from the 0 value
I think I understand how they find that value now
alright im gonna check my theory
Okay 👍
I think your collage wants you to do this using the TI-84 calculator
instead of calculating it by hand
and sadly I don't know how to do it with calculator :(
the different b value is caused by the calculator being able to do more calculations for the value
a more exact value that is
And I sadly have to go ;/
Good luck though
I got 442.89
Okay thanks
Shit man. If anyone is still here now that he left, I’m still just a bit confused on some things.
Anyone?
.close
Closed by @fading narwhal
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Help quick
Do you know what 12.3x10^8 is
No
Wait lemme put it in a calculator
A number is usually written in scientific notation when a number between 1 and 10 is multiplied by a power of 10.
In your case, 12.3 * 10^8 can be written as 1.23 * 10^9
But that isn't important
You are pretty much multiplying two numbers written in scientific notation
So (a number times a power of 10) times (a number times a power of 10)
What 12.3 * 10^8 means is just that you are multiplying 12.3 with 100.000.000 (notice the 8 zeroes)
If you had for example 5 * 10^4, this would mean 5 * 10.000 (5 zeroes), or 50.000
Anyway
You see that there's just a bunch of multiplication involved.
If you need to solve this without a calculator, you need to know a few properties that multiplication and exponents have and this is a piece of cake
Otherwise you can just plug it in a calculator ... 🙃
mention me when you get back if you need me please
@elder field Has your question been resolved?
Closed by @elder field
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• Show your work, and if possible, explain where you are stuck.
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Hello! I’ve been stuck on this for awhile. I think I’ve got the function and the other answers, but they rely on my function being correct, so I just want someone to help me fact check my answers.
(a) Function: y = 442.89(1.074^x)
(b) 15722.077
(c) 2008
I’m just gonna assume that nobody is active. I’ve made three different channels trying to get this one problem, and the only helper I’ve gotten was also confused so we mutually decided to get a different set of eyes on this problem. I’ve been waiting 2 hours. I’ll try later today.
It might be easy to set up a LinearRegression model for this in Python.
Your equation is not right
Assuming ur suppose to use a regression line
I tried a regression line in desmos and it didn’t appear to be accurate
What did u do to get the equation u got
I used a TI84 calculator and used ExpReg
ok. I did not use a calculator and idk how it works. I can help u do it calculatorless if u want though
Let’s do that so that I can make sure my answers are correct
Ok so linear regression line is of the form y=a+bx
We are given the data is exponential though so we need to transform it a bit
First step is to take the log of all the income. This will make the relation ship between year and log(personal income) linear
so log(y)=a+bx is what we are finding a and b for now
b=cov(x,log(y)), a = mean(log(y)) - b * mean(x)
find that out then sub back into the equation and solve for y
in general, x is independent var, y is dependent var. b is usually given by cov(x,y)/var(x,y), but we needed to modify it cuz we transformed y values to log. a is usually given by mean(y)-b(mean(x)) but we needed to modify it again cuz we transformed y values to log
you find a and b using these equations
Im sorry, everything is looking like word soup to me right now, i'm confused
Did you learn about how to manually find linear regression lines or were u told to just use calculator
my professors taught me on the calculator and on desmos
im not sure what var and cov are
okay thank you, sorry that i dont know these things
nvm im dumb. Im getting the same thing.
So I was correct?
Yeah
yeah
15722.0778 rounded 3 decimal places to 15722.078
I dont think I rounded my year up, I rounded down
shit am i messing up
54.7 on the graph is when I reach 22000
so 1955
plus 54.7 is 2009.7
Yah
am I doing this wrong, it would round up right? cause its closer to 2010
it says to round up, so the answer is actually 2010?
Maybe u could round up. I would say round down since its during the year 2009 that it is reached
like 8 months into 2009 they reach 22tril
The problem specifically says round up to the nearest year in the directions, so would I do 2009 or 2010
okay so in totality
y=442.89(1.074^x)
15722.078
2010
i think that all checks out
yeah