Determine if the expression is a perfect square and if it is, factor it.
a2 – 8a + 16
a.
(a + 4)(a – 4)
b.
(4a + 1)2
c.
(a – 4)(a – 4)
d.
not a perfect square

The answer is C. With FOIL, F would be a*a (a^2), O would be a*-4 (-4a), I would be -4*a (-4a), and L would be -4*-4 (16). Both -4a and -4a have the same variable (a) so would combine to make -8a. You would then end up with a^2-8a+16.