Question

\(\left|7-a\right|=9\)

Answer 1

\(\left|7-a\right|=9\)

\(\Rightarrow\left[{}\begin{matrix}7-a=9\\7-a=-9\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}a=-2\\a=16\end{matrix}\right.\)

Vậy: \(x\in\left\{-2;16\right\}\)

Answer 2

Answer 3

<=>\(\left[{}\begin{matrix}7-a=9\\7-a=-9\end{matrix}\right.\)

<=>\(\left[{}\begin{matrix}a=-2\\a=16\end{matrix}\right.\)