Question

Como resolver x2 + x =20

Answer 1

x² - x - 20 = 0

a = 1

b = -1

c = -20

Δ = b² - 4ac

Δ = (-1)² - 4.1.(-20)  

Δ = 1 + 80

Δ = 81

x = -b ± √Δ / 2a

x = -(-1) ± √81 / 2.1

x = 1  ± 9 / 2

x' = 1 + 9 / 2 = 10 / 2 = 5

x'' = 1 - 9 / 2 = -8 / 2 =  -4

S{5, -4}