Answer
All real numbers except $x=2$ and $x=-5$
Work Step by Step
$\frac{x^2-1}{x^2+3x-10}$
The denominator can not be equal to zero:
$x^2+3x-10\ne0$
$x^2+5x-2x-10\ne0$
$x(x+5)-2(x+5)\ne0$
$(x-2)(x+5)\ne0$
$x\ne2$ and $x\ne-5$
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