1 $\int\limits_{0}^{2}(3x+1)dx=(\frac{3x^2}{2}+x)\int\limits_{0}^{2}=8$2,$\int\limits_{-\sqrt{2}}^{\sqrt{2}}\sqrt{2-x^2}dx$
đặt $x=\sqrt{2}\sin t\Rightarrow dx=\sqrt{2}\cos tdt$
$\Rightarrow 2\int\limits_{-\frac{\Pi }{2}}^{\frac{\Pi }{2}}\cos^2 tdt$
ok nhé