\(4-2\left(x+1\right)=x\)
\(4-2x+2=x\)
\(-2x-x=-4-2\)
\(-3x=-6\)
\(x=2\)
Vậy pt có nghiệm là 2
\(4-2\left(x+1\right)=-x\)
\(\Leftrightarrow4-2x-2=-x\)
\(\Leftrightarrow2-2x+x=0\)
\(\Leftrightarrow2-x=0\)
\(\Leftrightarrow x=2\)
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\(x+\left(x+1\right)+\left(x+2\right)+...+\left(x+19\right)+\left(x+20\right)=20\)
\(\Leftrightarrow\left(x+x+x+...+x\right)+\left(1+2+3+...+20\right)=20\)
\(\Leftrightarrow21x+210=20\)
\(\Leftrightarrow21x=-190\)
\(\Leftrightarrow x=\frac{-190}{21}\)