ta123
need help on the attachment @Calculus1
Delete
Share
This Question is Closed
ta123
Best Response
You've already chosen the best response.
1
ta123
Best Response
You've already chosen the best response.
1
hey you know on the other problem you were helping me with lagrange?
ta123
Best Response
You've already chosen the best response.
1
what did you get for the answer because I got -4 and they counted it wrong
LagrangeSon678
Best Response
You've already chosen the best response.
1
i got 2
LagrangeSon678
Best Response
You've already chosen the best response.
1
are u sure you evaluated correctly
ta123
Best Response
You've already chosen the best response.
1
oh, made a stupid sign error
ta123
Best Response
You've already chosen the best response.
1
could you help me with this new problem on the attachment
LagrangeSon678
Best Response
You've already chosen the best response.
1
yeah let me look at it
LagrangeSon678
Best Response
You've already chosen the best response.
1
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
ta123
Best Response
You've already chosen the best response.
1
ok
LagrangeSon678
Best Response
You've already chosen the best response.
1
|dw:1321490017407:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
|dw:1321490044699:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
|dw:1321490067161:dw|
ta123
Best Response
You've already chosen the best response.
1
do you replug the original function into u after integrating
LagrangeSon678
Best Response
You've already chosen the best response.
1
yes after you, integrate, you must replace the orginal function
ta123
Best Response
You've already chosen the best response.
1
did you get u^2/2-3x*2U^(1/2) after integrating
LagrangeSon678
Best Response
You've already chosen the best response.
1
give me a sec
LagrangeSon678
Best Response
You've already chosen the best response.
1
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|
LagrangeSon678
Best Response
You've already chosen the best response.
1
okay, now you should get:|dw:1321490948435:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
now let fix up that integral:|dw:1321491019469:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
|dw:1321491091199:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
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
LagrangeSon678
Best Response
You've already chosen the best response.
1
now simply we have:|dw:1321491263984:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
next you have to integrate that, and then replace the u's. Then evaluate over your limits
LagrangeSon678
Best Response
You've already chosen the best response.
1
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
ta123
Best Response
You've already chosen the best response.
1
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?
LagrangeSon678
Best Response
You've already chosen the best response.
1
on top we had u^2-3, cause we replaced the x remeber
ta123
Best Response
You've already chosen the best response.
1
oh, ok also you forgot to label the endpoints on the integral
LagrangeSon678
Best Response
You've already chosen the best response.
1
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
ta123
Best Response
You've already chosen the best response.
1
I got -44
ta123
Best Response
You've already chosen the best response.
1
is that right?
ta123
Best Response
You've already chosen the best response.
1
???
LagrangeSon678
Best Response
You've already chosen the best response.
1
yes i did,1 is the correct answer
ta123
Best Response
You've already chosen the best response.
1
Thanks could you help me with one more of these problem?
LagrangeSon678
Best Response
You've already chosen the best response.
1
sure
LagrangeSon678
Best Response
You've already chosen the best response.
1
did you post it already?
ta123
Best Response
You've already chosen the best response.
1
LagrangeSon678
Best Response
You've already chosen the best response.
1
i cant open it
ta123
Best Response
You've already chosen the best response.
1
ta123
Best Response
You've already chosen the best response.
1
could you open it?
LagrangeSon678
Best Response
You've already chosen the best response.
1
yeah, okay lets do this, can we multiply the x into the brackets, then seperate the integral into two spereate integrals:|dw:1321500013159:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
now lets take out some constants:
|dw:1321500075388:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
now let try this, can we for the first integral, let x^2=u, then du=2xdx, which further means du/2x=dx
LagrangeSon678
Best Response
You've already chosen the best response.
1
now it should look something like this:|dw:1321500219046:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
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|
LagrangeSon678
Best Response
You've already chosen the best response.
1
now 2*1/2 is simply 1, so we now have:|dw:1321500384165:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
now we can integrate
LagrangeSon678
Best Response
You've already chosen the best response.
1
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
LagrangeSon678
Best Response
You've already chosen the best response.
1
|dw:1321500486597:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
|dw:1321500522223:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
but lets replace the u:|dw:1321500561883:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
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|
LagrangeSon678
Best Response
You've already chosen the best response.
1
furthermore:|dw:1321500784828:dw|
LagrangeSon678
Best Response
You've already chosen the best response.
1
Got it
ta123
Best Response
You've already chosen the best response.
1
yes, I was just was reviewing all the work, thanks!
LagrangeSon678
Best Response
You've already chosen the best response.
1
anytime:)soon you will be an expert on calculus and you will be helping others as well
ta123
Best Response
You've already chosen the best response.
1
I hope so, thanks again
LagrangeSon678
Best Response
You've already chosen the best response.
1
your welcome:)