Question

Rút gọn biểu thức : a)(x-1)^3-x(x-2)^2+x-1 b)(x-1)^3-(x+1)^3+6(x+1)(x-1)

Answer 1

a) (x - 1)³ - x(x - 2)² + x - 1

= x³ - 3x² + 3x - 1 - x(x² - 4x + 4) + x - 1

= x³ - 3x² + 3x - 1 - x³ + 4x² - 4x + x - 1

= x² - 2

b) (x - 1)³ - (x + 1)³ + 6(x + 1)(x - 1)

= x³ - 3x² + 3x - 1 - x³ - 3x² - 3x - 1 + 6x² - 6

= -8

Answer 2

a: \(=x^3-3x^2+3x-1-x\left(x^2-4x+4\right)+x-1\)

\(=x^3-3x^2+4x-2-x^3+4x^2-4x=x^2-2\)

b: \(=x^3-3x^2+3x-1-x^3-3x^2-3x-1+6\left(x^2-1\right)\)

=-6x^2-2+6x^2-6

=-8