Question

tìm x:

|x| - 7 = 9

9 - 25 = (7 - x) - (25 + 7)

Answer 1

\(\left|x\right|-7=9\Rightarrow\left|x\right|=16\)

\(\Rightarrow x=\pm16\)

\(9-25=\left(7-x\right)-\left(25+7\right)\)

\(9-25=7-x-25-7\)(tính chất mở ngoặc đôie dấu)

\(9-25=-x-25\)

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

\(\Rightarrow x=-9\)

Vậy x = - 9

Answer 2

\(a.\)

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

\(\Rightarrow\left|x\right|=9+7=16\)

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

\(b.\)

\(9-25=\left(7-x\right)-\left(25+7\right)\)

\(\Leftrightarrow9-25=7-x-25-7\)

\(\Rightarrow-16=-x-25\)

\(\Rightarrow-x=-16+25=9\)

\(\Rightarrow x=-9\)