The value of x is equal to 1.
(x + 4)^2 - (x - 5)^2 = 9
Expand.
(x + 4)(x + 4) - (x - 5)(x - 5) = 9
FOIL.
x^2 + 4x + 4x + 16 - (x^2 - 5x - 5x + 25) = 9
Distribute -1 to each term inside parentheses.
x^2 + 4x + 4x + 16 - x^2 + 5x + 5x - 25 = 9
Combine like terms.
18x - 9 = 9
Add 9 to both sides.
18x = 18
Divide both sides by 18.
x = 1
