#### Answer

$a^2+2ab+b^2$;
squared;
product of the first and second terms;
squared

#### Work Step by Step

RECALL:
$(a+b)^2=a^2+2ab+b^2.$
Thus, the missing words/expression in the given statement (in order) are
$a^2+2ab+b^2$;
squared;
product of the first and second terms;
squared.