Answer
$(b+4+a)(b+4-a)$
Work Step by Step
Recognize $b^{2}+8b+16=(b+4)^{2}$
$b^{2}+8b+16-a^{2}=(b+4)^{2}-a^{2}$
... and this is a difference of squares, $A^{2}-B^{2}=(A-B)(A+B)$
$=[(b+4)+a][(b+4)-a]$
$=(b+4+a)(b+4-a)$
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