Hi,

I'm trying to solve this integral

$\displaystyle \int_{0}^{0.4}12.5x(1-x)^4 dx$

I'm letting u = 1-x, so that I have

$\displaystyle \int_{0.6}^{1}12.5(1-u)u^4 du$

Then

$\displaystyle 2.5u^5 - \frac{25}{12}u^6 |^{1}_{0.6} =0.3195$

But if I replace u with 1-x then

$\displaystyle 2.5(1-x)^5 - \frac{25}{12}(1-x)^6 |^{0.4}_{0}$

I don't get the correct answer.

Why is this? Can I not substitute (1-x) for u?

Thanks.