Bài 1 :
a) 2(x - 5) - 2 = 8 - x
2x - 10 - 2 + x = 8
3x - 12 = 8
3x = 20
x = 20/3
b) (x + 1)(x + 2) + (3 - x)(x + 4) = 6
x^2 + x + 2x + 2 + 3x - x^2 + 12 - 4x = 6
(x^2 - x^2) + (3x + 2x + x - 4x) + 12 + 2 = 6
2x + 14 = 6
2x = 20
x = 10
c) x(x - 3) + (x - 3) = 0
(x + 1)(x - 3) = 0
TH1 : x + 1 = 0 => x = -1
TH2 : x - 3 = 0 => x = 3
d) 5(x - 3) - x^2 + 3x = 0
5(x - 3) - x(x - 3) = 0
(5 - x)(x - 3) = 0
TH1 : 5 - x = 0 => x = 5
TH2 : x - 3 = 0 => x = 3
e) x^2 - 5x + 6 = 0
x^2 - 2x - 3x + 6 = 0
x(x - 2) - 3(x - 2) = 0
(x - 3)(x - 2) = 0
TH1 : x - 3 = 0 => x = 3
TH2 : x - 2 = 0 => x = 2
f) x^2 + 4x + 4 = 1
(x + 2)^2 = 1
=> x + 2 = 1
x = -1
