y=(2x+2/3-5/3)/(3x+1)
=(2x+2/3)/(3x+1)-(5/3)/(3x+1)
=2(x+1/3)/[3(x+1/3)]-5/(9x+3)
=2/3-5/(9x+3)
因为5/(9x+3)≠0
所以y≠2/3
值域(-∞,2/3)∪(2/3,+∞)