\(\dfrac{x-1}{-15}=\dfrac{-60}{x-1}\)
\(\Rightarrow\left(x-1\right)\left(x-1\right)=\left(-60\right)\left(-15\right)\)
\(\Rightarrow\left(x-1\right)^2=900\)
\(\Rightarrow\left(x-1\right)^2=\pm30^2\)
\(\Rightarrow\left[{}\begin{matrix}x-1=30\\x-1=-30\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=31\\x=-29\end{matrix}\right.\)
\(\dfrac{x-1}{-15}=\dfrac{-60}{x-1}\)
\(\Leftrightarrow\left(x-1\right)\left(x-1\right)=\left(-15\right)\left(-60\right)\)
\(\Leftrightarrow\left(x-1\right)^2=900\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left(x-1\right)^2=30^2\\\left(x-1\right)^2=\left(-30\right)^2\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x-1=30\\x-1=-30\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=31\\x=-29\end{matrix}\right.\)
Vậy ................
