#### Answer

$(2-b^n)(2+b^n)$

#### Work Step by Step

RECALL:
A difference of two squares can be factored using the formula:
$x^2-y^2=(x-y)(x+y)$
The given binomial can be written as:
$=(2)^2-(b^n)^2$
This binomial is a difference of two squares.
Factor the given difference of two squares using the formula above with $x=2$ and $y=b^n$ to obtain:
$=(2-b^n)(2+b^n)$