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Every difference of squares problem can be factored as follows: a2 – b2 = (a + b)(a – b) or (a – b)(a + b). So, all you need to do to factor these types of problems is to determine what numbers squares will produce the desired results.
F(6) means f times 6 so f6
27
18
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45
GCF of 45 = 15
Here is a word document on Greatest Common Factors and how to solve it.
