Làm tính nhân
a) \(\left(-5x^2\right)\left(3x^3-2x^2+x-1\right)\)
\(=-15x^5+10x^4-5x^3+5x^2\)
b) \(\left(-4^3+\frac{2}{3}y-\frac{1}{4}yz\right)\left(-\frac{1}{2}xy\right)\)
\(=\left(-64+\frac{2}{3}y-\frac{1}{4}yz\right)\left(-\frac{1}{2}xy\right)\)
\(=32xy-\frac{1}{3}xy^2+\frac{1}{8}xy^2z\)