Question

Phân tích đa thức thành nhân tử:

a) 5x² – 10x b) x² – y² – 2x + 2y c) 4x² – 4xy – 8y²

 

Answer 1

a) 5x² - 10x = 5x( x - 2 )

b) x² - y² - 2x + 2y = (x² - y²) - (2x - 2y)

                             = (x - y ) ( x + y)-2 (x-y)

                             = ( x - y) ( x + y - 2)

c) 4x² - 4xy - 8y² = (4x² - 4xy + 8y²) - 9y²

                           = (2x - 9y²) - 3y²

                           = (2x - y - 3y) (2x - y + 3y)

                           = (2x - 4y) (2x + 2y)

                            = 4(x - 2y) (x + y)

Answer 2

a) 5x² - 10x = 5x( x - 2 )

b) x² - y² - 2x + 2y = (x² - y²) - (2x - 2y)

                             = (x - y ) ( x + y)-2 (x-y)

                             = ( x - y) ( x + y - 2)

c) 4x² - 4xy - 8y² = (4x² - 4xy + 8y²) - 9y²

                           = (2x - 9y²) - 3y²

                           = (2x - y - 3y) (2x - y + 3y)

                           = (2x - 4y) (2x + 2y)

                            = 4(x - 2y) (x + y)

Answer 3

a) 5x² - 10x = 5x( x - 2 )

b) x² - y² - 2x + 2y = (x² - y²) - (2x - 2y)

                             = (x - y ) ( x + y)-2 (x-y)

                             = ( x - y) ( x + y - 2)

c) 4x² - 4xy - 8y² = (4x² - 4xy + 8y²) - 9y²

                           = (2x - 9y²) - 3y²

                           = (2x - y - 3y) (2x - y + 3y)

                           = (2x - 4y) (2x + 2y)

                            = 4(x - 2y) (x + y)