若3的x次方等于2,12的y次方等于8,则1/x-3/y等于?用指数函数知识解决

答：
3^x=2，12^y=8
x=log3(2)，y=log12(8)
1/x-3/y
=1/log3(2)-3/log12(8)
=log2(3)-3log8(12)
=log2(3)-3log2(12)/log2(8)
=log2(3)-3log2(12)/3
=log2(3/12)
=log2(1/4)
=-2
是否可以解决您的问题？

3^x=2 3=2^(1/x)
12^y=8 12=8^(1/y) =2^(3/y)
3/12=2^(1/x-3/y) 1/x-3/y=log2 (1/4)=-2

3^x=212^y=8=2^3=(3^x)^3=3^3x 12^y=(3*4)^y=(3^y)*[(2^2)^y]=(3^y) * (2^2y)=(3^y) * (3^x)^2y=(3^y)*(3^2xy)=3^(y+2xy)=3^3x所以 y+2xy=3xy-3x=-2xy1/x - 3/y=(y-3x)/xy = -2xy/xy=-2

3的x次方等于2，可得x=log3为底2
12的y次方等于8,可得y=log12为底8
所以，1/x-3/y=1/log3为底2-3/log12为底8
=log2为底3-3log8为底12
=log2为底3-log2为底12
=log2为底(3/12)
=-2