domain restrictions

Since  the numerator is a polynomial, it won't have any domain restrictions

The domain restrictions  will occur when an x value makes the denomiantor = 0

So...to find these values, set the denominator to 0  and solve for x

x^2 + 2x  - 3    = 0     factor

(x + 3) ( x - 1)  = 0

Set each factor to  0  and solve for x

x + 3  = 0                 x - 1  = 0   

x  = -3                       x  = 1

So  x cannot be  -3    or   1