Question 175676
{{{x^2+6x+9-a^2}}}


The trick with this one is to recognize that {{{x^2+6x+9}}} is a perfect square, namely {{{(x + 3)^2}}}.


That means that the entire expression is the difference of two squares:


{{{(x + 3)^2-a^2}}} which can be factored {{{((x + 3) + a)((x + 3) - a)}}}