10ab-3+6b-5a-2b^3+b^2
=10ab-5a+6b-3-2b^3+b^2
=5a(2b-1)+3(2b-1)-b^2(2b-1)
=(2b-1)(5a+3-b^2)
原式=[a^(n+2)-a^n]-(a^2-2a+1)
=a^n(a²-1)-(a-1)²
=a^n(a+1)(a-1)-(a-1)²
=(a-1)[a^n(a+1)-(a-1)]
=(a-1)[a^(n+1)+a^n-a+1]