y=2/x-1 +1/5-x=[2/x-1 +1/5-x]×4/4=1/4×[2/x-1 +1/5-x]×[(x-1)+(5-x)]=1/4×[2+1+2(5-x)/(x-1)+(x-1)/(5-x)]≥1/4×[3+2√2(5-x)/(x-1)×(x-1)/(5-x)]=1/4(3+2√2)故函数的最小值为1/4(3+2√2)。
