9^x+4^x=5/2* 6^x两边同时除以6^x得：（3/2)^x+(2/3)^x=5/2令t=(3/2)^x, 则方程化为;t+1/t=5/2t^2-5/2*t+1=0(t-2)(t-1/2)=0t=2 , 或1/2故(3/2)^x=2或1/2x=ln2/(ln3-ln2) 或x=-ln2(ln3-ln2)