已知a-b=1,a方+b方=25,求ab的值
a-b=1
(a-b)方=1方
a方-2ab+b方=1
25-2ab=1
2ab=24
ab=12
1.x(x+y)-y(x+y)
=(x+y)(x-y)
2.(a+b)方+2(a+b)+1
=[(a+b)+1]方
=(a+b+1)方
3.4x方-4x的立方+x方
=5x方-4x的立方
=x方(5-4x)
4.x方-16ax+64a方
=(x-8a)方
5.（x-1)(x-3)+1
=x方-4x+3+1
=x方-4x+4
=(x-2)方
6.(ab+a)+(b+1)
=[a(b+1)+(b+1)
=(b+1)(a+1)