Question

Solve this equation using an algebraic method: (x + 4)( x - 4) = 9

Answer 1

(x+4) (x-4) = 9
x^2 -4x+4x -16 = 9
x^2 -16 = 9
x^2 = 9+16
x = √25
x = +5 & -5
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Answer 2

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

Using the identity, a² - b² = (a + b)(a - b),

=> x² - 16 = 9
=> x² = 9 + 16
=> x² = 25
=> x = +5 or -5

∴ Value of x = +5 or -5