(4a+1)^2-2(4a+1)+1=(4a+1-1)^2=16a^2
(2+a)^3-a^3=2*(a^2+a(2+a)+4+a^2+4a)=2(3a^2+6a+4)
(a-1)^3+(x+1)^3=(a+x)(a^2-2a+1+x^2+1+2x-ax+1+x-a)=(a+x)(a^2+x^2-2a+2x-ax+x-a+3)
a^2+b^2-2ab-c^2=(a-b)^2-c^2=(a-b+c)(a-b-c)
16(x-y)^2-25(x+y)^2=(4(x-y)+5(x+y))(4(x-y)-5(x+y))=(9x+y)(-x-9y)
4b^4-4b^2+1-c^2=(2b^2-1)-c^2=(2b^2+c-1)(2b^2-c-1)