Question 190302
a^2 - a - 20/a^2 - 16 divided by a-5 
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Factor where you can to get:
= [(a-5)(a+4)]/[(a-4)(a+4)]/(a-5)
Invert the denominator and multiply to get:
= [(a-5)(a+4)]/[(a-4)(a+4)]*[1/(a-5)]
Cancel factors that are common to a numerator and a denominator
such as (a+4), (a-5)
= [1/(a-4)]
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Cheers,
Stan H.