Question

Tìm xZ, biết:

 a)2x+5=x-1

 b)2011+2010+2009+...+x=2011

Mn làm xong nhanh giúp mik với ạ. Thanks nhiều!

Answer 1

\(a,2x+5=x-1\)

\(2x+5-\left(x-1\right)=0\)

\(2x+5-x+1=0\)

\(2x-x=0-5-1\)

\(x=-6\)

Answer 2

a) 2x+5=x- 1

     2x-x=-1-5

      X=-6

Answer 3

a) \(2x+5=x-1\)

\(\Leftrightarrow2x+5-x=-1\)

\(\Leftrightarrow x+5=-1\)

\(\Leftrightarrow x=-6\)

Vậy \(x=-6\)

b) \(2011+2010+2009+...+x=2011\)

\(2011+\left(2010+2009+...+x\right)=2011\)

\(2010+2009+...+x=2011-2011\)

\(2010+2009+...+x=0\)

Từ \(2010\rightarrow x\)có x số

\(\Leftrightarrow2x+2010.x=0\)

\(\Leftrightarrow x+2010.x=0\)

\(\Leftrightarrow x+2010=0\)

\(\Leftrightarrow x=-2010\)

Vậy \(x=-2010\)