#### Answer

$(a-b+2)(a+b-2)$

#### 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 the given difference of two squares using the formula above with $x=a$ and $y=b-2$ to obtain:
$=[a-(b-2)][a+(b-2)]
\\=(a-b+2)(a+b-2)$