a, /a-1/ -x + 1=0
TH1: a - 1 = 0 => a = 1
TH2 : x + 1 = 0 =>x = -1
Vậy \(x\in\left\{1;-1\right\}\)
c)
| x + 7 | = | x - 9 |
TH1: x + 7 = x - 9
0x = -16 => Vô nghiệm
TH2: x + 7 = -x + 9
2x = 2
=> x = 1
Vậy x = 1
\(\left|2-x\right|+2=x\)
\(\Rightarrow\left|2-x\right|=x-2\)
\(\Rightarrow\orbr{\begin{cases}2-x=x-2\\2-x=2-x\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}-x-x=-2-2\\-x+x=2-2\end{cases}\Rightarrow\orbr{\begin{cases}-2x=-4\\0=0\left(loại\right)\end{cases}\Rightarrow}x=2}\)