Question

Tìm số nguyên x biết 

4-2(x+1)=-x

X+(x+1)+(x+2)+....+(x+19)+(x+20)=20

Answer 1

\(4-2\left(x+1\right)=x\)

\(4-2x+2=x\)

\(-2x-x=-4-2\)

\(-3x=-6\)

\(x=2\)

Vậy pt có nghiệm là 2 

Answer 2

\(4-2\left(x+1\right)=-x\)

\(\Leftrightarrow4-2x-2=-x\)

\(\Leftrightarrow2-2x+x=0\)

\(\Leftrightarrow2-x=0\)

\(\Leftrightarrow x=2\)

Answer 3

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Answer 4

\(x+\left(x+1\right)+\left(x+2\right)+...+\left(x+19\right)+\left(x+20\right)=20\)

\(\Leftrightarrow\left(x+x+x+...+x\right)+\left(1+2+3+...+20\right)=20\)

\(\Leftrightarrow21x+210=20\)

\(\Leftrightarrow21x=-190\)

\(\Leftrightarrow x=\frac{-190}{21}\)