\(\frac{x}{-4}=\frac{-9}{x}\)
\(\Rightarrow x.x=\left(-9\right).\left(-4\right)\)
\(\Rightarrow x^2=36\)
\(\Rightarrow x^2=6^2=\left(-6\right)^2\)
\(\Rightarrow\orbr{\begin{cases}x=6\\x=-6\end{cases}}\)
Vậy \(x\in\left\{6;-6\right\}\)
Ta có :
\(-4\times\left(-9\right)=36.\)
Mà \(x\times x=36\)
Mà \(-6\times-6=36\)
\(6\times6=36\)
\(\Rightarrow x=\left\{6;-6\right\}\)