Đáp án:
1.
b, 4x(3x-5)-2(4x+1)-(x+7)
=4x.3x-4x.5-2.4x-2-x-7
=12x²-20x-8x-x-9
=12x²-29x-9
c, (-3x²+$\frac{2}{3}$ xy-y²)( $\frac{-1}{2}$ xy)
=(-3x² . $\frac{-1}{2}$ xy+ $\frac{2}{3}$xy . $\frac{-1}{2}$ xy+ y². $\frac{1}{2}$ xy
=$\frac{3}{2}$ . x³y -$\frac{1}{3}$ . x²y² +$\frac{1}{2}$ xy³
d, x(x³+x²+x+1)-(x³+x²+x+1)
=x^4 + x³+x²+x-x³-x²-x-1
=x^4 -1
