a, \(\left(x-3\right)\left(6x^2-2x+1\right)=6x^3-2x^2+x-18x^2+6x-3=6x^3-20x^2+7x-3\)
b, \(\left(\frac{1}{2}xy-1\right)\left(2x^2y+y\right)=x^3y^2+\frac{xy^2}{2}-2x^2y-y\)
c, \(\left(x^2y^2-3xy+2x\right)\left(x-3y\right)=x^3y^2-3x^2y^3-3x^2y+9xy^2+2x^2-6xy\)