` a) ` ` x^3 - 6x^2 + 12x - 8 `
` = x^3 - 3.x^2 . 2 + 3.x.2^2 - 2^3 `
` = (x - 2)^3 `
` b) ` ` -8x^3 + 12x^2 - 6x + 1 `
` = -[(2x)^3 - 3.(2x)^2 . 1 + 3.2x.1^2 - 1^3] `
` = -(2x - 1)^3 `
` c) ` ` x^3 - 3/2 x^2 y + 3/4 xy^2 - 1/8 y^3 `
` = x^3 - 3.x^2 . 1/2 y + 3.x. (1/2 y)^2 - (1/2 y)^3 `
` = (x - 1/2 y)^3 `
` d) ` ` (x - y)^3 + 6(x - y)^2 + 12(x - y) + 8 `
` = (x - y)^3 + 3.(x - y)^2 .2 + 3.(x - y).2^3 + 2^3 `
` = (x - y + 2)^3 `
Áp dụng hằng đẳng thức:
` a^3 + 3a^2 b + 3ab^2 + b^3 = (a + b)^3 `
` a^3 - 3a^2 b + 3ab^2 - b^3 = (a - b)^3 `
