Question

Use completing the square to solve (x – 12)(x + 4) = 9 for x.

Answer 1

OK, here we go
open brackets first,
X²+4x-12x-48=9
x²-8x-48-9=0
x²-8x-57=0
x²-8x=57
x²-8x-4²=57-4²
(x-4)²=57-16
(X-4)²=41
√(x-4)²=+ or -√41
x=4+√41 or x=4-√41
x=4+6.403 or x=4-6.403
x=10.403 or -2.403
x≈ 10.4 or -2.4