Question 189833
{{{7a^2-28b^2}}} Start with the given expression



{{{7(a^2-4b^2)}}} Factor out the GCF 7



{{{7(a^2-(2b)^2)}}} Rewrite {{{4b^2}}} as {{{(2b)^2}}}



{{{7(a+2b)(a-2b)}}} Factor {{{a^2-(2b)^2}}} to get {{{(a+2b)(a-2b)}}} (note: use the difference of squares formula)



So {{{7a^2-28b^2}}} completely factors to {{{7(a+2b)(a-2b)}}}