应该是x＜5/4,
4x-5<0
5-4x>0
y=4x-2+1/4x-5
=(4x-5)+1/(4x-5)+3
=-[(5-4x)+1/(5-4x)]+3
<=-2*根号[(5-4x)*1/(5-4x)]+3=-2+3=1
(5-4x)^2=1,x=1时,取=号.
所以y的最大值=1