Answer
All real numbers apart from $1$ and $-2$.
Work Step by Step
We know that for rational expressions the domain is all the real numbers, excluding when the denominator is $0$.
$x^2+x-2=x^2-x+2x-2=x(x-1)+2(x-1)=(x-1)(x+2)$
Here the denominator is $0$, when $x=1$ or $x=-2$, thus the domain is all real numbers apart from $1$ and $-2$.