4a²-(1+a²-b²)²
=(2a-1-a+b²)(2a+1+a-b²)
=(a-1+b²)(3a+1-b²)
x⁴+1/64
=x⁴+1/4x²+1/64-1/4x²
=(x²+1/8)²-1/4x²
=(x²-1/2x+1/8)(x²+1/2x+1/8)
c²+a(a-2c)-(a²+d²-b²-c²)²
=c²+a²-2ac-(a²+d²-b²-c²)²
=(a-c)²-(a²+d²-b²-c²)²
=(a-c-a²-d²+b²+c²)(a-c+a²+d²-b²-c²)
4(ad+bc)²-(a²+d²-b²-c²)²
=(2ad+2bc-a²-d²+b²+c²)(2ad+2bc+a²+d²-b²-c²)
=[(b+c)²-(a-d)²][(a+d)²-(b-c)²]
=(b+c-a+d)(b+c+a-d)(a+d-b+c)(a+d+b-c)
