$-2x^{2}+40x=-30x-10x^{2}$
$8x^{2}+40x=-30x$
$8x^{2}+70x=0$
$x_{1,2}=\frac{-70\pm \sqrt{70^{2}-4\cdot 8\cdot 0}}{2\cdot 8}$
$x_{1,2}=\frac{-70\pm 70}{2\cdot 8}$
$x_{1}=\frac{-70+70}{2\cdot 8},x_{2}=\frac{-70-70}{2\cdot 8}$
$=0$
$=-\frac{35}{4}$
$x=0,x=-\frac{35}{4}$