Question 472768
This is example of difference of two squares  {{{a^2-b^2}}}
Steps to solve it:
find the square roots of the perfect squares, then 
one factor is their SUM  (a+b)
and the other factor is the DIFFERENCE between them (a-b)

then
{{{y^2-1=y^2-1^2=(y-1)(y+1)}}}