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Kim, There is another method you can use if you don't see the factors. The method is to complete the square. Again this works nicely if the coefficient of the square term is 1. Let's look at Stephen's example
To complete the square using the terms r^{2} + 6r I add the square of half the coefficient of the linear term, so here I add (6/2)^{2} = 32 = 9 since r^{2} + 6r + 9 = (r + 3)^{2}. Because I am going to add 9 to the expression I need to subtract 9 also to maintain the equality.
If you recognize this as a difference of squares you can continue
Penny  


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