Question

What number goes in the box so that \[x^2 + 18x + \boxed{\phantom{00}}\]is the square of a binomial? If you find more than one, give your answer as a list.

Answer 1

81

Explanation:

x² + 18x

x² + 2(x)(9) + 9²

x² + 2(x)(9) + 81

(x + 9)²