a=0,f(x)=x+5,f(x)在区间（1/2,1)上是增函数a≠0,f(x)=ax^2-(a-1)x+5=a[x-(0.5-0.5a)]^2-(a^2-22a+1)/(4a)对称轴x=0.5-0.5a讨论：（1）a>0,则抛物线开口向上,对称轴x≤1/2,即0.5-0.5a≤1/2,a≥0,则函数f(x)=ax2-(a-1...