(a-1)²-(b-2a)(2-b)
=a²-2a+1-(2b-b²-4a+2ab)
=a²-2a+1-2b+b²+4a-2ab
=(a²-2ab+b²)+(2a-2b)+1
=(a-b)²+2(a-b)+1
=(a-b+1)²
x^n+1 -4x^n
=x^n·x-4x^n
=x^n(x-4)
(a-1)²-(b-2a)(2-b)
=a²-2a+1-(2b-b²-4a+2ab)
=a²-2a+1-2b+b²+4a-2ab
=(a²-2ab+b²)+(2a-2b)+1
=(a-b)²+2(a-b)+1
=(a-b+1)²
x^n+1 -4x^n
=x^n·x-4x^n
=x^n(x-4)