y=(4x^2+8x+13)/6(x+1)
6y(x+1)=4x^2+8x+13
4x^2+(8-6y)x+13-6y=0
方程有解,则判别式>=0
即:(8-6y)^2-4*4(13-6y)>=0
64-96y+36y^2-208+96y>=0
36y^2>=144
y^2>=4
y>=2或y