Solve this equation: (x + 4)(x - 4) = 9

Solution:

Given equation is

(x + 4)(x - 4) = 9

We know (a + b)(a - b) = a² - b², is the difference of squares.

Therefore

(x + 4)(x - 4) = x² - 16

Hence,

x² - 16 = 9

x² = 16 + 9

x² = 25

x = ± 5

Solve this equation: (x + 4)(x - 4) = 9

Summary:

On solving this equation (x + 4)(x - 4) = 9 we obtain x = ± 5.