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Messages - Sang Wu

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1
FE / Re: FE1
« on: December 14, 2014, 06:57:05 PM »
Hi prof, I think if we substitute x = 0, y = 3 into U, we should get C = 54 instead of 18.

2
FE / Re: FE3
« on: December 14, 2014, 06:55:52 PM »
Hi Prof, I think c2 should be e^t - ln(1+e^t) rather than +.

3
TT1 / Re: TT1-problem 2
« on: October 09, 2014, 08:32:54 PM »
a. W = x2(lnx + 1)
b. W= xy2' - y2 = x2(lnx + 1)
    u = e^(∫-1/x * dx) = x^(-1)
    (y2/x)' = lnx + 1
    y2/x = ∫(lnx + 1)dx = ∫lnxdx + x = xlnx - x + x = xlnx

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