$\displaystyle \int_{-18}^1 s\, \left|81 - s^2\right|\, ds$ =

$\displaystyle \int_{0}^{81 \pi^2} \frac{\sin(\sqrt{x})}{\sqrt{x}}\,dx$ =

$\displaystyle \int_{9}^{18}\frac{t-9}{t^2-18 t +82}\,dt$ =