Question

-х в квадрате+7х+8=0

Answer 1

$-x {}^{2} + 7x + 8 = 0 \\ D = 7 {}^{2} - 4 \times 8 \times ( - 1) = 49 + 32 = 81 \\ x = \frac{ -7 - 9}{ - 2} \: \: x = \frac{ -7 + 9}{ - 2} \\ x = 8 \: \: \: \: \: \: x = - 1$

Ответ: -1;8

Answer 2

-x²+7x+8=0

x²-7x-8=0

D=49+32=81=9²

x=(7±9)/2

x1=8;x2=-1