



 
Hi Minks, It is often easier to find the values of $x$ that are not in the domain of the function, that is the values of $x$ for which the function doesn't yield a legitimate value. Look at your function \[\frac{x^2 + 1}{x^2 +2x  3} \times \frac{x^2 9}{x^2  2x  3}.\] If you substitute a value of $x$ into this expression you get a real number except if one on the denominators is zero. Factor both denominators, find the values of $x$ that make the denominators zero and then the domain of the function is all real numbers $x$ except the ones that make a denominator equal to zero. I hope this helps,  


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