#### Answer

(a) square of a binomial

#### Work Step by Step

RECALL:
(1) $(a+b)^2$ is a square of a binomial
(2) $(a+b)(a-b)$ is the product of the sum and difference of the same two terms
The given expression is in the same form as the one in part (1) above.
Thus, the given expression is a square of a binomial.