<PRE><B>Question 549364</B>
Factor Completely 

81c^2-121
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Both 81c^2 and 121 are perfect squares.
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{{{81c^2-121 = (9c)^2 - 11^2}}}
The difference of the squares of 2 terms is the sum times the difference.
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= (9c + 11)*(9c - 11)
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