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Mathematics 11 Online
OpenStudy (anonymous):

calculus help

OpenStudy (anonymous):

Go ahead :D

OpenStudy (anonymous):

OpenStudy (anonymous):

can you help me with no 10

OpenStudy (anonymous):

anyone?

OpenStudy (anonymous):

both parts?

OpenStudy (anonymous):

just one

OpenStudy (anonymous):

part A?

OpenStudy (anonymous):

yes please

OpenStudy (anonymous):

Okay :)

OpenStudy (anonymous):

Well, what you have is an initial value problem. So, as you may know, when you take an antiderivative (or integrate a function) you always have a +C at the end. Well, initial value problems help you solve the exact C value. So for the one you're given f'(x)=1/x^2+x you want to first integrate it. \[f(x)=\int\limits x^{-2}+x dx\] \[f(x)=-x^{-1}+(1/2)x^2+C\]

OpenStudy (anonymous):

From here, you want to plug in your initial value. Namely, f(2)=1. \[f(2)=-(1/2)+(1/2)(2^2)+C\] That has to equal 1. or \[f(2)=-(1/2)+(1/2)(2^2)+C=1\] adding the 1/2 and multiplying out the 2^2 and the (1/2) you get: \[(3/2)=2+C \rightarrow C=-(1/2)\]

OpenStudy (anonymous):

Any questions? :P

myininaya (myininaya):

i was totally confused there are two number 10s

OpenStudy (anonymous):

I did part A. Where are you confused?

OpenStudy (anonymous):

i am confused what you did at adding and multiplying

OpenStudy (anonymous):

where is the equation?

OpenStudy (anonymous):

where did you get 3/2 at the left?

OpenStudy (anonymous):

Okay. That is just 1+(1/2)

myininaya (myininaya):

no i'm not confused about what you did i was confused which problem to do

OpenStudy (anonymous):

A is done you could help me with B

OpenStudy (anonymous):

what problem do you want me to solve?

OpenStudy (anonymous):

pat, I just wanted you to solve A. I think myini is doing B

OpenStudy (anonymous):

A for number 10?

OpenStudy (anonymous):

yes. The answer was c=-1/2 right?

OpenStudy (anonymous):

Yes :)

myininaya (myininaya):

\[\frac{d^2y}{dt^2}=2-6t\] \[frac{dy}{dt}=2t-\frac{6t^2}{2}+C_1\] \[\frac{dy}{dt} (at; t=0)=2(0)-3(0)^2+C_1=4, C_1=4\] \[y(t)=\frac{2t^2}{2}-\frac{3t^3}{3}+4t+C_2\] \[y(0)=0^2-0^3+4(0)+C_2=1\] \[C_2=1\] y(t)=t^2-t^3+4t+1

OpenStudy (anonymous):

\[\int\limits_{?}^{?}(x ^{-2}+x)dx\] =\[=(x ^{-1})/-1 + (x ^{2})/2\] =\[-x ^{-1}+(x ^{2})/2\] + c 1=-1/2 + 2 + c c=1+1/2-2 c=-1/2

myininaya (myininaya):

my latex messed up on line two can you make it out?

OpenStudy (anonymous):

i cant understand the third one myininaya

myininaya (myininaya):

i evaluated y' at t=0 becuase we are given y'(0)=4

OpenStudy (anonymous):

hey pat, x>0 right? so how is answer less than 0? I did this stuff at begining of the year so i am really confused

OpenStudy (anonymous):

yeah, i am sorry. i forgot

OpenStudy (anonymous):

yeah, x>0, and we have x=2

OpenStudy (anonymous):

how 2?

OpenStudy (anonymous):

thanks myininaya for B

myininaya (myininaya):

:)

OpenStudy (anonymous):

pat, you there?

OpenStudy (anonymous):

myininaya if you still there can you look ar pats solution and say how is the ansewer 2?

myininaya (myininaya):

its c=-1/2 f(x)=-1/x+x^2/2-1/2

myininaya (myininaya):

is that your question?

OpenStudy (anonymous):

yes thanks

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