\(\frac{x+3}{-8}=\frac{-18}{x+3}\Leftrightarrow\left(x+3\right)\left(x+3\right)=\left(-18\right).\left(-8\right)=144\)
\(\Rightarrow\left(x+3\right)^2=144=12^2\Leftrightarrow x+3=12\)
\(\Rightarrow x=12-3=9\) Vậy \(x=9\)
Ta có: \(\frac{x+3}{-8}=\frac{-18}{x+3}\)
\(\Rightarrow\left(x+3\right).\left(x+3\right)=-18.\left(-8\right)\)
\(\Rightarrow\left(x+3\right)^2=144\)
\(\Rightarrow\left(x+3\right)^2=\left(\pm12\right)^2\)
\(\Rightarrow\orbr{\begin{cases}x+3=12\\x+3=-12\end{cases}\Rightarrow\orbr{\begin{cases}x=9\\x=-15\end{cases}}}\)
\(\Rightarrow x\in\left\{-15;9\right\}\)
_Học tốt-.-_
