Question 467456
When adding and subtracting fractions, you have to get a common denominator.
To do that, all of the denominators need to be completely factored:


5/(a - 3) - 2/(aČ - 9) 
= 5/(a - 3) - 2/(a + 3)(a - 3) {factored aČ - 9 into two binomials}
= 5(a + 3)/(a + 3)(a - 3) - 2/(a + 3)(a - 3) {got common denominator of (a + 3)(a - 3)}


5(a + 3) - 2
------------- {combined numerators over common denominator}
(a + 3)(a - 3)


5a + 15 - 2
-------------- {used distributive property in numerator}
(a + 3)(a - 3)


5a + 13
-------------- {combined like terms in numerator}
(a + 3)(a - 3)
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