Question

Bài 1 thực hiện phép tính 

1) (x^2-2x-1).(x-3)

2) (-x+4).(-x^2+4x-1)

3) (2x-1).(x^2-5x+3)

Answer 1

1) (x² - 2x - 1)(x - 3)

= x²(x - 3) - 2x(x - 3)  - 1(x - 3)

= x³ - 3x² - 2x² + 6x - x + 3

= x³ - 5x² + 5x + 3

2. (-x + 4)(-x² + 4x - 1)

= -x(-x² + 4x - 1) + 4(-x² + 4x - 1)

= x³ - 4x² + x - 4x² + 16x - 4

= x³ - 8x² + 17x - 4

3 ) (2x - 1)(x² - 5x + 3)

= 2x(x² - 5x + 3) - 1(x² - 5x + 3)

= 2x³ - 10x²  + 6x - x² + 5x - 3

= 2x³ - 11x² + 11x - 3

Answer 2

            Bài làm :

1) (x² - 2x - 1)(x - 3)

= x²(x - 3) - 2x(x - 3)  - 1(x - 3)

= x³ - 3x² - 2x² + 6x - x + 3

= x³ - 5x² + 5x + 3

2) (-x + 4)(-x² + 4x - 1)

= -x(-x² + 4x - 1) + 4(-x² + 4x - 1)

= x³ - 4x² + x - 4x² + 16x - 4

= x³ - 8x² + 17x - 4

3 ) (2x - 1)(x² - 5x + 3)

= 2x(x² - 5x + 3) - 1(x² - 5x + 3)

= 2x³ - 10x²  + 6x - x² + 5x - 3

= 2x³ - 11x² + 11x - 3