Cách làm cho bạn:
a) x$^{3}$(3x$^{2}$ - x - $\frac{1}{2}$) = 3x$^{5}$ - x$^{4}$ - $\frac{1}{2}$x$^{3}$;
b) (5xy - x$^{2}$ + y)$\frac{2}{5}$xy$^{2}$ = 2x$^{2}$y$^{3}$ - $\frac{2}{5}$x$^{3}$y$^{2}$ + $\frac{2}{5}$xy$^{3}$;
c) (4x$^{3}$ - 3xy$^{2}$ + 2xy)(-$\frac{1}{3}$x$^{2}$y) = -$\frac{4}{3}$x$^{5}$y + x$^{3}$y$^{3}$ -$\frac{2}{3}$x$^{3}$y$^{2}$.
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