Question

a) l 4x - 8 l = 7
b) x la a 2 - 9x + 8 = 0

Answer 1

a) │4x - 8 │= 7 ⇔ 4x - 8 = 7 sau 4x - 8 = -7

4x - 8 = 7 
4x = 7+8
4x = 15
x=15/4

4x - 8 = -7
4x = - 7 + 8
4x = 1
x = 1/4

x∈{1/4, 15/4}


b) x² - 9x + 8 = 0

x² - 9x + 8 = x² - x - 8x + 8 =
                 = x(x-1) - 8(x-1) =
                 = (x-1)(x-8)

Egalăm fiecare factor cu 0.

x-1=0 ⇒ x₁ = 1
x-8=0 ⇒ x₂ = 8