Question

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

With complete method...

Answer 1

x(x-4)+4(x-4)=9
x²-4x+4x-16=9
x²-16=9
x²=16+9
x²=25
x=√(25)
x=5

Answer 2

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

We know that ( a + b )( a - b ) = a² - b²

⇒ x² - 4² = 9

⇒ x² - 16 = 9

⇒ x² = 9 + 16

⇒ x² = 25

⇒ x = ± √25

⇒ x = ± 5

The value of x is + 5 or - 5 .