\(A=\dfrac{x-5}{\left|5-x\right|}=-1\)
\(\Rightarrow-1\left|5-x\right|=x-5\Rightarrow\left|5-x\right|=5-x\)
\(\Rightarrow x\le5\)
\(A=\dfrac{x-5}{\left|5-x\right|}=-1\)
\(\Leftrightarrow x-5=-1\left|5-x\right|\)
\(\Leftrightarrow x-5=-5+x\)
\(\Leftrightarrow x-x-5=-5\)
\(\Rightarrow0-5=-5\)
Thỏa mãn với mọi x