y=(5x-1)/(4x+2)
y(4x+2)=5x-1
4yx+2y=5x-1
(4y-5)x=-1-2y
x=(2y+1)/(5-4y)
分母≠0
即5-4y≠0
y≠5/4
值域为（-∞,5/4）U(5/4,+∞)