a)
4x^2 - 3x(7-2x)+5x=4x^2-21x+6x^2+5x=10x^2-16x=2x(5x-8)
d)
7x-2(x+3)(5-x)=7x-2(5x-x^2+15-3x)=7x-2(2x-x^2+15)=
=7x-4x+2x^2-30=2x^2+3x-30
e)
8x(1-x^2)- (x-7)(-3x^2)=8x-8x^3-(-3x^3+21x^2)=8x-8x^3+3x^3-21x^2=
=-5x^3-21x^2+8x=x(-5x^2-21x+8)
f)
1-4 (x^2 - x+2)(1+x)=1-4(x^2+x^3-x-x^2+2+2x)=1-4(x^3+x+2)=
=1-4x^3-4x-8=-4x^3-4x-7