Question

Tìm x, biết :

​/x+1/+/x+4/=3x

Answer 1

TH1 : \(x< -4;\)ta có:

\(-\left(x+1\right)+\left[-\left(x+4\right)\right]=3x\)

\(-2x-5=3x\)

\(-2x-3x=5\)

\(-5x=5\)

\(x=-1\)(không thỏa mãn )

TH2 : \(-4\le x< -1;\)ta có:

\(-\left(x+1\right)+\left(x+4\right)=3x\)

\(3=3x\)

\(x=1\)( không thỏa mãn)

TH3 : \(x\ge-1;\)ta có:

\(\left(x+1\right)+\left(x+4\right)=3x\)

\(2x+5=3x\)

\(x=5\)(thỏa mãn)

Vậy \(x=5\).