How do you factor $49a^2 - 81b^2$ ?

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Answer 1 · 2015-07-09T13:57:53

You may notice that $49=7^2and81=9^2$ are both squares.

So $49a^2=(7a)^2and81b^2=(9b)^2$ are also squares, and then we can use the special product of the form: $x^2-y^2=(x+y)(x-y)$

$=(7a+9b)(7a-9b)$

How do you factor 49a^2 - 81b^249a^2 - 81b^2?