y=(5x-1)/(4x+1)值域,

y=(5x-1)/(4x+1)
=(5x+5/4-9/4)/(4x+1)
=(5x+5/4)/(4x+1)-(9/4)/(4x+1)
=5/4 -(9/4)/(4x+1)
∵ 4x+1≠0
∴ -(9/4)/(4x+1)≠0
∴ y≠5/4
即值域为{y|y≠4/5}