Bài 1:
` a) ` ` 25x^3 - 25x^{2}y - x + y `
` = 25x^3 - x - 25x^{2}y + y `
` = x(25x^2 - 1) - y(25x^2 - 1) `
` = (25x^2 - 1)(x - y) `
` = (5x - 1)(5x + 1)(x - y) `
Câu b sửa đề ạ !
` b) ` ` x^2 - 3x + 2 `
` = x^2 - x - 2x + 2 `
` = x(x - 1) - 2(x - 1) `
` = (x - 1)(x - 2) `
Bài 2:
` a) ` ` x^3 - 3x^2 - 16x + 48 = 0 `
` <=> x^{2}(x - 3) - 16(x - 3) = 0 `
` <=> (x^2 - 16)(x - 3) = 0 `
` <=> (x - 4)(x + 4)(x - 3) = 0 `
` TH1: `
` x - 4 = 0 `
` => x = 4 `
` TH2: `
` x + 4 = 0 `
` => x = -4 `
` TH3: `
` x - 3 = 0 `
` => x = 3 `
Vậy ` x = 4 ` hay ` x = -4 ` hoặc ` x = 3 `
` b) ` ` 10x^2 - 33x - 7 = 0 `
` <=> 10x^2 + 2x - 35x - 7 = 0 `
` <=> 2x(5x + 1) - 7(5x + 1) = 0 `
` <=> (2x - 7)(5x + 1) = 0 `
` TH1: `
` 2x - 7 = 0 `
` <=> 2x = 7 `
` <=> x = 7/2 `
` TH2: `
` 5x + 1 = 0 `
` <=> 5x = -1 `
` <=> x = -1/5 `
