x²/9+16/x²=（-10/3）(x/3-4/x)令x/3-4/x=t,则x²/9+16/x²=)=(x/3-4/x)²+8/3=t²+8/3=(-10/3)tt²+10t/3+8/3=03t²+10t+8=0(3t+4)(t+2)=0t=-4/3或t=-2于是x/3-4/x=-4/3或x/3-4/...