Answer
$(x-4a)(x+4a)+7(2x+7)$
Work Step by Step
$ x^{2}+14x+49-16a^{2}\qquad$...factor in pairs.
$=(x^{2}-16a^{2})+(14x+49)\qquad$...recognize the difference of two squares: $a^{2}-b^{2}=(a-b)(a+b)$
$=(x-4a)(x+4a)+7(2x+7)$
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