## Calculus 10th Edition

$8$
Use u-substitution to integrate the function $\int_0^8 (\frac{2x}{\sqrt {x^2 +36}}) dx$, let $u=x^2+36$ $\int_0^8 u^{-\frac{1}{2}} du$ $[2u^{\frac{1}{2}}]_0^8$ $[2\sqrt {x^2 +36} ]_0^8$ $(2\sqrt {100} - 2\sqrt {36})$ $20-12= 8$