# Integration problem

Hello, I am trying to integrate the following using "u-substitution", however I am not getting the correct result. Can someone please advise where I am going wrong.
The following is my attempt:

x(x-1)^3

u = x-1

du/dx = 1
du/1 = dx

x(u)^4 / 4

My final (incorrect) answer.
x(x-1)^4 / 4

## Answers and Replies

tiny-tim
Science Advisor
Homework Helper
hello fran1942!

(try using the X2 button just above the Reply box )
x(u)^4 / 4

no, you must substitute every x …

you can't end up with something that still has an x in it!

You should rewrite the equation. If you foil out the (x-1)3 to x3-3x2+3x-1 then multiply by the x to get x4-3x3+3x2-x I think you will have an easier time integrating and without using a u-sub.

Don't forget the constant of integration!

we cannot seem to integrate plancks law to show that stefans boltzman constant is 5.67x10^-8