a, 3x (x − 1) − 1 + x = 0
3x ( x - 1 ) + ( x -1 ) =0
(x-1) ( 3x + 1 ) = 0
TH1 x- 1 = 0 TH2 3x -1 = 0
x = 1 3x = 1

x = 1/3

vậy x = 1 hoặc x= 1/3

b, x^2 - 9x = 0
x ( x-9 ) =0
TH1 x=0 TH2 x-9=0
x = 9

vậy x = 0 hoặc x = 9

a,(2x + 1)^2 = 2x^2 + 2.2x.1 + 1^2
b, ( a - b/2)^3 = a^3 - 3a^2b + 3ab^2 - b^2

a, x^2 + 25 - 10x = x^2 - 10x +25
= x^2 - 2.x.5 + 5^2
= (x - 5)

b,-8y^3 + x^3 = x^3 - 8y^3

= x^3 - (2y)^3
= (x-2y)[x^2 + x . (2y)+(2y)^2]
= (x - 2y)(x^2 + 2xy+4y^2)