X2-x - (a2-a) factorization, Is the sum of the squares of X and the square of A,

X2-x - (a2-a) factorization, Is the sum of the squares of X and the square of A,

x²-x-(a²-a)
=x²-x-a²+a
=(x²-a²)-(x-a)
=(x+a)(x-a)-(x-a)
=(x-a)(x+a-1)
Prompt: after grouping, extract the common factor: x-a