According to the properties of a logarithm, when we have a multiplication in the argument of this function we can write it as the sum of logartihms, like this:
[tex]\log_a(x\times y)=\operatorname{\log}_a(x)+\operatorname{\log}_a(y)[/tex]
Then, we can apply this property to the given logarithm to get:
[tex]\log_3(81x)=\log_3(81)+\log_3(x)[/tex]
