Question 614662: If y=x over x2-9, what is the value of y when x = -3 ?
Answer by rapaljer(4671)   (Show Source):
You can put this solution on YOUR website! 
When you substitute x=-3, because you have x^2-9 in the denominator, you have to square the value of -3, which is (-3)^2, which is 9. Then, the total denominator is 9-9, which is 0. You are NEVER allowed to divide by ZERO, so the answer is UNDEFINED!!
I have some problems like this on my website if you are interested in seeing it. To find my website, use the easy-to-spell and easy-to-remember link www.mathinlivingcolor.com. This link takes you to a single page with a single link near the bottom of the page. Click on this link, and it takes you to my Homepage.
Once you are on my Homepage, look for "Basic, Intermediate, and College Algebra: One Step at a Time." Choose "Basic Algebra", and look in "Chapter 1," for "Section 1.05 Variables and Substitution." In particular, Problem #27 in this section is VERY similar to your problem. This very problem is then solved IN COLOR on the Math in Living Color page for "Basic Algebra", Section 1.05. Check it out!! Math is usually not as hard as it looks!!
Dr. Robert J. Rapalje, Retired
Seminole State College of Florida
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