c)-5x(x²-2x-1)=-5x³+10x²+5x
d) (3-x)(x²+8x+16)=3x²+24x+48-x³+8x³+16x=3x²+7x³+40x+24
e) (x²-3x-10)(x²-5x)=x⁴-5x³-3x³+15x²-10x²-50x=x⁴-8x³+5x²-50x
f) (x²-10)(3x²-20)=3x⁴-20x²+30x²-200=3x⁴+10x²-200
g) (x²-x)(-x²+2x+11)=-x⁴+2x³+11x²+x²-2x²-11x=x⁴+2x³+10x²
h) (x²-4x-5)(x²+3x-4)=x⁴+3x³-4x²-4x³-12x²+8x-5x²-15x+20=x⁴-x³-21x²-7x+20