Rút gọn biểu thức: a) A = (x - 2)(x + 2)(x + 3) - $(x + 1)^{3}$ b) B = $(x + 2)^{3}$ - $(x - 2)^{3}$ - $12x^{2}$

Đáp án:

 `↓↓↓`

Giải thích các bước giải:

 `a,A = (x - 2)(x + 2)(x + 3) - (x + 1) ^ 3`$\\$`A = (x ^ 2 - 4)(x + 3) - (x ^ 3 + 3x ^ 2 + 3x + 1)`$\\$`A = x ^ 3 + 3x ^ 2 - 4x - 12 - x ^ 3 - 3x ^ 2 - 3x - 1`$\\$`A = 3x ^ 2 - 4x - 12 - 3x ^ 2 - 3x - 1`$\\$`A = - 4x - 12 - 3x - 1`$\\$`A = - 7x - 12 - 1`$\\$`A = - 7x - 13`$\\$`b,B = (x + 2) ^ 3 - (x - 2) ^ 3 - 12x ^ 2`$\\$`B = x ^ 3 + 6x ^ 2 + 12x + 8 - (x ^ 3 - 6x ^ 2 + 12x - 8) - 12x ^ 2`$\\$`B = x ^ 3 + 6x ^ 2 + 12x + 8 - x ^ 3 + 6x ^ 2 - 12x + 8 - 12x ^ 2`$\\$`B = 6x ^ 2 + 12x + 8 + 6x ^ 2 - 12x + 8 - 12x ^ 2`$\\$`B = 6x ^ 2 + 8 + 6x ^ 2 + 8 - 12x ^ 2`$\\$`B = 0 + 8 + 8`$\\$`B=0+16`$\\$`B=16`