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hey you know on the other problem you were helping me with lagrange?
what did you get for the answer because I got -4 and they counted it wrong
i got 2
are u sure you evaluated correctly
oh, made a stupid sign error
could you help me with this new problem on the attachment
yeah let me look at it
okay so this is what you wanna do, set u=x+4, then you have to then rewrite x in terms of u. You can do this simply by saying x=u-4
do you replug the original function into u after integrating
yes after you, integrate, you must replace the orginal function
did you get u^2/2-3x*2U^(1/2) after integrating
give me a sec
i led you wrong, my mistake. What you want to do, is let u=sqrt(x+4), now we rewrite x interm of u. To do this simply:|dw:1321490856188:dw|
okay, now you should get:|dw:1321490948435:dw|
now let fix up that integral:|dw:1321491019469:dw|
now recall that u=sqrt(x+4), thus we can divide out the u in the denmominator and the sqrt(x+4) as so:|dw:1321491198348:dw| The two can be put outside the integral since it is a constant
now simply we have:|dw:1321491263984:dw|
next you have to integrate that, and then replace the u's. Then evaluate over your limits
or, we could simply change the limits interms of u. Which would actaully be much eaier in this case. But i leave that up to you to decide on
sqrt(x+4) did both cancel out and when you replace the u on the bottom back to x+4 don't you have to do the same thing to the top?
on top we had u^2-3, cause we replaced the x remeber
oh, ok also you forgot to label the endpoints on the integral
well,i didnt forget, for me it is simpler to first leave the limits while i do the integration, since they really dont matter untill we get the antiderivative, which we then evlauate over the limits
I got -44
is that right?
yes i did,1 is the correct answer
Thanks could you help me with one more of these problem?
did you post it already?
i cant open it
could you open it?
yeah, okay lets do this, can we multiply the x into the brackets, then seperate the integral into two spereate integrals:|dw:1321500013159:dw|
now lets take out some constants: |dw:1321500075388:dw|
now let try this, can we for the first integral, let x^2=u, then du=2xdx, which further means du/2x=dx
now it should look something like this:|dw:1321500219046:dw|
now we see that the x will divide out, and the 1/2 from the du can be taken outside the integral, so now we will get :|dw:1321500319063:dw|
now 2*1/2 is simply 1, so we now have:|dw:1321500384165:dw|
now we can integrate
for the first integral, what i the antiderivative of f'? well its simply f, the orginal function , and the second integral is very simpyle to integrate
but lets replace the u:|dw:1321500561883:dw|
now you can evaluate this over you limits but remeber that you were given certain conditions, namely f(1)=3 and f(0)=1.so we have|dw:1321500688385:dw|
yes, I was just was reviewing all the work, thanks!
anytime:)soon you will be an expert on calculus and you will be helping others as well
I hope so, thanks again