y=(3x^2+3x+1)/(x^2+x-1) =[3(x^2+x-1)+4]/(x^2+x-1)=3+4/(x^2+x-1)
x^2+x-1≥-5/4
y≤-1/5或y≥3
.y=x+√(2x-1)为增函数,x≥1/2,y≥1/2