\(\frac{x}{-4}=\frac{9}{x}\)
x.x=(-4).9
x.x=-36
\(x^2=-36\)
x= -6
\(\frac{x}{-4}=-\frac{9}{x}\Rightarrow\frac{x.x}{-4x}=\frac{-9.-4}{-4x}\Rightarrow x^2=36=\left(6\right)^2=\left(-6\right)^2\)
=> x = 6 hoặc x= -6
\(\frac{x}{-4}=-\frac{9}{x}\Rightarrow x^2=36\Rightarrow x=+-6\)