Question 147452
{{{a^2-9}}} Start with the given expression


{{{(a)^2-9}}} Rewrite {{{a^2}}} as {{{(a)^2}}}


{{{(a)^2-(3)^2}}} Rewrite {{{9}}} as {{{(3)^2}}}



Now use the difference of squares. Remember, the difference of squares formula is {{{A^2-B^2=(A+B)(A-B)}}} where in this case {{{A=a}}} and {{{B=3}}}


{{{a^2-9=(a+3)(a-3)}}} Plug in {{{A=a}}} and {{{B=3}}}


So the expression


{{{a^2-9}}}


factors to


{{{(a+3)(a-3)}}}


Notice that if you foil the factored expression, you get the original expression. This verifies our answer.