Answer
$$(1+9y)(1-9y)$$
Work Step by Step
$1-81y^{2}$
This is the difference between two squares.
There is a simple formula for this case:
$x^{2}-y^{2}=(x+y)(x-y)$
So, applying this formula,
We need to take the square of both terms.
$\sqrt 1=1$
$\sqrt 81y^{2}=9y$
So the answer would look like:
$$(1+9y)(1-9y)$$
(One with a positive sign and one with a negative sign.)
