令x/3-4/x=t
x^2/9+16/x^2=(10/3)(x/3-4/x)=(x/3-4/x)^2+8/3
t^2+8/3-10/3t=0
3t^2-10t+8=0
(3t+2)(t-2)=0
t=-3/2,t=2
然后……