Concept:
Derivative of function involving modulus fails where expression inside modulus becomes zero and changes sign.
Step 1: Factor modulus expression.
Inside modulus
\[
x^2+x-6
\]
Factorize
\[
=(x+3)(x-2)
\]
Zeros occur at
\[
x=-3,\qquad x=2
\]
Step 2: Analyze differentiability.
Absolute value function changes sign at roots.
Derivative fails at points where modulus changes sign.
Thus derivative undefined at
\[
x=-3,\qquad x=2
\]
Step 3: Write domain.
Hence derivative exists everywhere except these points.
\[
Domain=
\mathbb R-\{-3,2\}
\]
Therefore
\[
\boxed{\mathbb R-\{-3,2\}}
\]