How do you factor $4x^2 - 81$ ?

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Answer 1 · 2015-11-14T04:09:16

$color(blue)((2x+9)(2x-9)$

$4x^2−81$ can also be expressed as
$(2x)^2-9^2$

Now as per the property :
$color(blue)(a^2-b^2=(a+b)(a-b)$ we can re write the expression.

$color(blue)((2x)^2-9^2= (2x+9)(2x-9)$
(here $a=2x, b=9)$

So the factorised form for the expression is
$color(blue)((2x+9)(2x-9)$

How do you factor 4x^2 - 814x^2 - 81?