First, you should solve for

, which equals

. Now, solve the integral of

=

, to get that

. You can check this by taking the integral of what you got. Now by the Fundamental Theorem
![\int\limits^2_0 {4x} \, dx=[2x^2] ^(2)_(0)=2(2)^(2)-2(0)^2=8](https://img.qammunity.org/2016/formulas/mathematics/high-school/t261ssv2xbnzddabaclurv6pp1afmiycin.png)
.
This should be the answer to your question, if I understood what you were asking correctly.