设3X+4=T
4/T+T/3=3
12+T^2-9T=0
[T-4.5]^2=33/4
T-9/2=+/-根33/2
T=9/2+/-根33/2
3X+4=9/2+/-根33/2
X1=1/6+根33/6
X2=1/6-根33/6