3^a=5^b=M
a=log3(M)=lgM/lg3
b=log5(M)=lgM/lg5
1/a+1/b=2
lg3/lgM+lg5/lgM=2
2lgM=lg3+lg5
2lgM=lg15
M=√15
0
3^a=5^b=M
a=log3(M)=lgM/lg3
b=log5(M)=lgM/lg5
1/a+1/b=2
lg3/lgM+lg5/lgM=2
2lgM=lg3+lg5
2lgM=lg15
M=√15