Question

(x-1) (x.x+7) = (x-1) (5x+1)
Resposta: {1,2,3}

Answer 1

 (x-1) (x.x+7) = (x-1) (5x+1)

 x.x + 7 = 5x + 1 ==> x² - 5x + 1 - 7 = 0

x² - 5x - 6 = 0

Δ = (-5)² - 4.1.(-6) ==> 25 - 24 =  1

x= 5 +/- 1
         2

x1 = 5+1 ==> x1= 3  ; x2 = 5 - 1 ==> x2 = 2
          2                                  2
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x- 1 = 0 ==> x = 1