Find the area enclosed between and from to .

$\displaystyle \int_{-2}^{6} [(0.4^2+3) - (x)] dx$

$\displaystyle \frac {0.4x^3}{3} + 3x - \frac {x^2}{2}$

If I'm not mistaken, I now have to use the Fb - Fa formula. However, my answer turns out wrong so I'm assuming I made a mistake in the calculations shown above. Can someone please tell me where it is?