Giải thích các bước giải:
$(15+x):3=3^{15}:3^{12}$
$⇔15+x=3.3^{15}:3^{12}$
$⇔15+x=3^{16}:3^{12}$
$⇔15+x=3^4$
$⇔x=3^4-15$
$⇔x=81-15$
$⇔x=66$
$\text{Vậy $x=66$}$
$\text{b) Xem lại đề}$
$c)(2x-4)^2=64$
$⇔(2x-4)^2=±8$
$⇔$ \(\left[ \begin{array}{l}2x-4=8\\2x-4=-8\end{array} \right.\) $⇔$ \(\left[ \begin{array}{l}2x=12\\2x=-4\end{array} \right.\) $⇔$ \(\left[ \begin{array}{l}x=6\\x=-2\end{array} \right.\)
$\text{Vậy $x∈\{-2;6\}$}$
Học tốt!!!
