Solve the following equation:

(x + 3)(x - 3) = 40

Given, (x + 3)(x - 3) = 40.

⇒ x² - 3x + 3x - 9 = 40

⇒ x² - 9 = 40

⇒ x² - 9 - 40 = 0

⇒ x² - 49 = 0

⇒ x² - 7² = 0

By using, a² - b² = (a + b)(a - b) we get,

⇒ (x + 7)(x - 7) = 0

⇒ x + 7 = 0 or x - 7 = 0

⇒ x = -7 or x = 7.

Hence, roots of the given equations are -7, 7.