f(x)=ax^2-2ax+2+b=a(x-1)^2-a+b+2
顶点不在[2,3]上
当a>0时开口向上在[2,3]上单调递增
f(x)max=f(3)=5=3a+b+2
f(x)min=f(2)=2=b+2
a=1 b=0
当a