Question

Thực hiện phép nhân

a)(x+1)(x²+x+1)-(x+7)(x²-2)

b)(2x-7)²-2(7-2x)(5x+7)+(5x+7)²

c)(x+2)(x²-2x+4)-(1-x)(1+x+x²)

d)(3x-2)(3x+2)-9x(x+1)

e)(2x-3)(4x²+6x+9)-x(8x²+x-1)

Viết cách làm ra giúp mik. Cảm ơn mn nhìu.

Answer 1

a) (x + 1)(x² + x + 1) - (x + 7)(x² - 2)

= x³ + x² + x + x² + x + 1 - x³ + 2x - 6x² + 14

= -4x² + 4x + 15

b) (2x - 7)² - 2(7 - 2x)(5x + 7) + (5x + 7)²

= (2x - 7)² + 2(2x - 7)(5x + 7) + (5x + 7)²

= (2x - 7 + 5x + 7)²

= (7x)²

= 49x²

Answer 2

c) (x + 2)(x² - 2x + 4) - (1 - x)(1 + x + x²)

= (x³ + 2³) - (1 - x³)

= x³ + 8 - 1 + x³

= 2x³ + 7

d) (3x - 2)(3x + 2) - 9x(x + 1)

= (3x)² - 2² - 9x² - 9x

= 9x² - 4 - 9x² - 9x

= -9x - 4

Answer 3

e) (2x - 3)(4x² + 6x + 9) - x(8x² + x + 1)

= (2x)³ - 3³ - 8x³ - x² - x

= 8x³ - 27 - 8x³ - x² - x

= -x² - x - 27