c) \(\left|x^2-2x-3\right|+\left|x+1\right|=0\)
\(\Leftrightarrow\left|\left(x+1\right)\left(x-3\right)\right|+\left|x+1\right|=0\)
\(\Leftrightarrow\left|x+1\right|.\left(\left|x-3\right|+1\right)=0\)
\(\Leftrightarrow\left|x+1\right|=0\) ( Do \(\left|x-3\right|+1>0\) )
\(\Leftrightarrow x=-1\)
Vậy $x=-1$