已知3*9^m*27^m=3^21,则m=
问题描述:
已知3*9^m*27^m=3^21,则m=
答
3*9^m*27^m
=3*(3^2)^m*(3^3)^m
=3*3^2m*3^3m
=3^(1+2m+3m)
=3^21
1+2m+3m=21
m=4