Đáp án + Giải thích các bước giải:
$\text{a, (- 2x)($x^{3}$ - 3$x^{2}$ - x + 1)}$
$\text{ = -2$x^{4}$ + 6$x^{3}$ + 2$x^{2}$ - 2x}$
$\text{b, (-$\dfrac{1}{2}$xy)(-10$x^{3}$ + $\dfrac{2}{5}$y - $\dfrac{1}{3}$z)}$
$\text{ = 5$x^{4}$y - $\dfrac{1}{5}$x$y^{2}$ + $\dfrac{1}{6}$xyz}$
$\text{c, (-5$x^{3}$)(2$x^{2}$ + 3x -5)}$
$\text{ = -10$x^{5}$ - 15$x^{4}$ + 25$x^{3}$ }$
$\text{d, 2$x^{2}$ - $\dfrac{1}{3}$xy + $y^{2}$)(-3$x^{3}$) }$
$\text{= -6$x^{5}$ + $x^{4}$y - 3$x^{3}$$y^{2}$ }$
