Question

x²-6x+8 =

x²+10x+21=

x²-3x+21=

Answer 1

x^2-6x+8=0
x^2-4x-2x+8=0
x(x-4)-2(x-4)=0
(x-4)(x-2)=0
x=4, x=2

ou

x² - 6x + 8
x² - 6x + 8 = 0
∆ = b² - 4 . a . c
∆ = (-6)² - 4 . 1 . 8
∆ = 36 - 32
∆ = 4
x = (-b ± √∆) / 2a
x = [-(-6) ± √4] / (2 . 1)
x = (6 ± 2) / 2
x = 3 ± 1 [simplificando por 2]
x' = 3 + 1     x' = 4         x" = 3 – 1         x" = 2       S = {2, 4}

 

x^2 +10x +21= 0
(x+7)(x+3) = 0
x = -7 or x= -3

 

Falta fazer

x²-3x+21=