y=(3x+3/4+5/4)/(4x+1)
=(3x+3/4)/(4x+1)+(5/4)/(4x+1)
=3/4+(5/4)/(4x+1)
因为(5/4)/(4x+1)≠0
所以y≠3/4
值域(-∞,3/4)∪(3/4,+∞)