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

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