# how to integrate this??

• April 5th 2009, 12:54 PM
Arez
how to integrate this??
im trying to integrate the function $x(1-x)$ which is $x-x^2$. if I make u=x^2 or u=x-x^2 for u-substitution it never turns out right though.. please someone help
• April 5th 2009, 12:58 PM
Jhevon
Quote:

Originally Posted by Arez
im trying to integrate the function $x(1-x)$ which is $x-x^2$. if I make u=x^2 or u=x-x^2 for u-substitution it never turns out right though.. please someone help

u-substitution?! this is power rule!

remember, $\int x^n ~dx = \frac {x^{n + 1}}{n + 1} + C$ ........(for any constant $n \ne -1$ of course :D)

here you have $\int x^1~dx - \int x^2~dx$, just integrate each separately using the power rule
• April 5th 2009, 12:58 PM
Moo
Hello,

No, don't substitute anything (Surprised)

$\int x-x^2 ~dx=\int x ~dx-\int x^2 ~dx$

Then recall this common antiderivative :
$\int x^n ~ dx=\frac{x^{n+1}}{n+1}+C$, for any $n \neq 1$

Edit : woops, too late