How do you factor $0.09y^2 - 0.81$ ?

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Answer 1 · 2015-11-30T11:56:42

$0.09y^2 - 0.81 = (0.3y+0.9)(0.3y-0.9)$

The difference of squares formula gives us
$a^2 - b^2 = (a+b)(a-b)$
(you can multiply this out to confirm)

$0.09y^2 = (0.3y)^2$
and
$0.81 = 0.9^2$

Thus, by the difference of squares formula

$0.09y^2 - 0.81 = (0.3y+0.9)(0.3y-0.9)$

How do you factor 0.09y^2 - 0.810.09y^2 - 0.81?