a: Ta có: \(\left|x+1\right|+x=3\)
\(\Leftrightarrow\left|x+1\right|=3-x\)
\(\Leftrightarrow\left[{}\begin{matrix}x+1=3-x\left(x\ge-1\right)\\x+1=x-3\left(x< -1\right)\left(loại\right)\end{matrix}\right.\Leftrightarrow2x=2\)
\(\Leftrightarrow x=1\left(nhận\right)\)