Question

Menos vinte igual menos x menos x ao quadrado

Answer 1

-20=-x-x²
x²+x-20=0
x+x'=1
x.x'=20
4+(-5)=1
4.-5=-20
x'=4
x''=-5

Answer 2

-20 = -x - x²
x² + x -20 = 0
Δ = 1 - 4 . 1 . (-20)
Δ = 1 + 80 = 81
x1 = -1 + 9 / 2 = 8/2 = 4
x2 = -1 - 9 / 2 = -10/2 = -5