Đ​ặt​ \(A=\left|x+2\right|-\left|x+7\right|=0\)

* Với \(x< -7\) \(\Rightarrow A=-\left(x+2\right)-\left(-x-7\right)=0\)

\(\Rightarrow A=-x-2+x+7=0\)

\(\Rightarrow5=0\) ( KTMĐK )

* Với \(-7< x< -2\) \(\Rightarrow A=-\left(x+2\right)-\left(x+7\right)=0\)

\(\Rightarrow A=-x-2-x-7=0\)

\(\Rightarrow-2x-9=0\)

\(\Rightarrow-2x=9\)

\(\Rightarrow x=-\dfrac{9}{2}\) ( TMĐK )

* Với \(x>-2\) \(\Rightarrow A=\left(x+2\right)-\left(x+7\right)=0\)

\(\Rightarrow A=x+2-x-7=0\)

\(\Rightarrow-5=0\) ( KTMĐK )

Vậy : \(x=-\dfrac{9}{2}\)