设2^6a=3^3b=6^2c=A6a=log₂A3b=log₃A2c=log6 A 1/6a+1/3b-1/2c=1/log₂A+1/log₃A-1/log6 A=log(A)2+log(A)3-log(A)6=log(A)(2×3÷6)=log(A)(1)=0