_*(-.5)*_= -20
\(x (-0.5) x = -20 \)
\(-0.5{x}^{2}=-20\)
\({x}^{2}=\frac{-20}{-0.5}\)
\({x}^{2}=40\)
\(x=\sqrt{40}\)
\(x= 2\sqrt{10} , x=-2\sqrt{10}\)
