Using an algebraic method
Level
pending
Solve this equation (x + 4)( x - 4) = 9
x = 5 and x = -5
x = 5
x = 4 and x = -4
x = 9
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1 solution
(x-4) (x+4) = 9 Expand out terms of the left hand side: x^2-16 = 9 Add 16 to both sides: x^2 = 25 Take the square root of both sides: Answer: |x = 5 or x = -5|