3a^2-3=3*(a^2-1)=3*(a-1)(a+1)=(3a-3)(a+1)=3a^2+3a-3a-3=3a^2-3
2-2x^2=2*(1-x^2)=2*(1-x)(1+x)=(2-2x)(1+x)=2+2x-2x-2x^2=2-2x^2
5x^3-5x=5x*(x^2-1)=5x*(x-1)(x+1)=(5x^2-5x)(x+1)=5x^3+5x^2-5x^2-5x=
5x^3-5x
2x-8x^3=2x*(1-4x^2)=2x*(1-2x)(1+2x)=(2x-4x^2)(1+2x)=2x+4x^2-4x^2-8x^3=
2x-8x^3