Hmm. Looks good to me. Did they want you to expand the polynomials?
6561x^3-2187x^2+243x-9
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81x^2-18x+2
Or, since you flipped the limits of integration, that would change the sign of the answer, so it'd be +9*...
Let y = integrate from 1-9x to 1 of (u^3)/(1+u^2)
What is y'?
I flipped the integral so it's 1 to 1-9x and had the derivative of -9 via chain rule
so -9 and just plugged in 1-9x to the (u^3)/(1+u^2) so it's -9*((1-9x)^3)/(1+(1-9x)^2). It tells me what's wrong; but what is my error?
2 answers
Oh, thanks Steve! it's just the +9 that got me off track.