Answer
$b+3$;
$b-3$
Work Step by Step
RECALL:
A difference of two squares can be factored using the formula
$x^2-y^2=(x+y)(x-y)$
Factor using the formula above with $x=a$ and $y=b+3$ to obtain:
$=[a+(b+3)][a-(b+3)]
\\=(a+b+3)(a-b-3)$
Thus, the missing expressions in the given statement are:
$b+3$;
$b-3$
