(a-b+1)^2-(b-2a)(-b+2a)
=(a-b+1)²+(b-2a)²
=(a-b)²+2(a-b)+1+b²-4ab+4a²
=a²-2ab+b²+2a-2b+1+b²-4ab+4a²
=5a²-6ab+2b²+2a-2b+1