Question

|x-7|=x-7

Answer 1

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

\(\Rightarrow\hept{\begin{cases}x-7=x-7\\x-7=-x+7\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}x-x=-7+7\\x+x=7+7\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}0x=0\\2x=14\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}x\in N\\x=7\end{cases}}\)

Mà x<7 không thỏa mãn

\(\Rightarrow\hept{\begin{cases}x\in\left\{8,9,.....\right\}\\x=7\end{cases}}\)

Answer 2

/ x - 7 / = x - 7

TH1 : x - 7 = x - 7 .  Đk : x \(\ge7\)

=> 0x = 0

=> x = 0 

Th2 : - x + 7 = x - 7 .  Đk : x < \(7\)

=> -2x = -14 

=> x = 7