Đáp án:
Giải thích các bước giải:
$\text{a, 6(x³y+x-3)-6x(2xy²+1)-3x²y(2x-4y)}$
$\text{= 6x³y+6x-18-12x²y²-6x-6x³y+12x²y²}$
$\text{= (6x³y-6x³y)+(-12x²y²+12x²y²)+(6x-6x)-18}$
$\text{= -18}$
$\text{b, (x+a)(x-a)-x²(a+b)x}$
$\text{=x²-a²-x³(a+b)}$
$\text{= x²-a²-x³a-x³b}$
$\text{c, x-2(3x-1)(3x+1)+(x-1)}$
$\text{=x-2(9x²-1)+x-1}$
$\text{= x-18x²+2+x-1}$
$\text{= -18x²+2x+1}$