\(a,1+x=2\)
\(\Leftrightarrow x=2-1\)
\(\Rightarrow x=1\)
\(Do\)\(x\ne1\Rightarrow x\in\varnothing\)
Vậy \(x\in\varnothing\)
\(b,1-1=x\)
\(\Leftrightarrow0=x\)
\(\Leftrightarrow x=0\)
\(Do\)\(x\ne0\Rightarrow x\in\varnothing\)
Vậy \(x\in\varnothing\)