(1)f(x)=ax^2-2ax+2+b(a>0)
=a(x-1)^2-a+2+b
f(2)=2,f(3)=5
4a-4a+2+b=2,
9a-6a+2+b=5
a=1,b=0
(2)g(x)=x^2-2x+2-(m+1)x=x^2-(m+3)x+2
对称轴x=(m+3)/2.
[2,4]单调
(m+3)/2>=4或(m+3)/2=5或m