l o g 3 81 {\displaystyle log_{3}81}
l o g 3 81 l o g 3 3 4 {\displaystyle {\begin{aligned}log_{3}81\\log_{3}3^{4}\\\end{aligned}}}
על פי כלל הלוגרתם a b = x ⇔ log a ( x ) = b {\displaystyle a^{b}=x\Leftrightarrow \log _{a}(x)=b}
3 x = 3 4 x = 4 {\displaystyle {\begin{aligned}3^{x}=3^{4}\\x=4\end{aligned}}}
