因为对于任意实数a,b都满足式子,则假设a=b,则f(a-b)=f(0)
=1
=f(a)-b(2a-b+1)
=f(a)-a(2a-a+1)
=f(a)-a(a+1),所以1=f(a)-a(a+1)
所以f(x)=x(x+1)+1