Question

20 - 8x - x(в квадрате) = 0

Answer 1

$20 - 8x - x^{2} = 0$
$x^{2} +8x-20 = 0$
$D = 8^2 - 4*1*(-20) = 64+80 = 144 = 12^2$
$x_{1} = \frac{-8+12}{2} = \frac{4}{2} = 2$
$x_{2} = \frac{-8-12}{2} = \frac{-20}{2} = -10$

Ответ: -10; 2.