“What is the complete square of the expression x² + 18x + 81?”

"The expression x² + 18x + 81 is a perfect square trinomial. It follows the form (x + a)² = x² + 2ax + a² where 2a = 18 (so a = 9) and a² = 81. Thus the expression is (x + 9)². Recognizing perfect squares is essential in algebra simplifying factorization and solving quadratic equations with applications in fields like physics and computer graphics where quadratic forms model real-world phenomena."