Question

Calcule:
(x-1)(2x+1)=(x-1)(x+4)

Answer 1

Aplicar distributiva :

(x-1)(2x+1)=(x-1)(x+4) 
2x² + x - 2x - 1 = x² + 4x -x - 4 
2x² -x - 1 = x² + 3x - 4
2x² - x² -x - 3x -1 + 4 = 0
x² - 4x + 3 = 0

a = 1
b = -4
c = 3

Δ = b² -4 . a . c
Δ = (-4)² -4 . 1. 3
Δ = 16 - 12
Δ = 4

-b +- √Δ   /2.a

- (-4) +- √4   /2.1
4 +- 2   /2

x' = 4 + 2  /2
x' = 6/2
x' = 3

x" = 4 - 2  /2
x'' = 2  /2
x'' = 1

Resposta : S{ 1 , 3 }