Use completing the square to solve for  x  in the equation  (x - 12)(x + 4) = 9.a. x = -1 or 15b. x = 1 or 7c. x (plus sign over minus sign) square root of 41.d. x (plus sign over minus sign) square root of 73. this is timed!

Solve for x over the real numbers by completing the square:
(x - 12) (x + 4) = 9

Expand out terms of the left-hand side:
x^2 - 8 x - 48 = 9

Add 48 to both sides:
x^2 - 8 x = 57

Add 16 to both sides:
x^2 - 8 x + 16 = 73

Write the left hand side as a square:
(x - 4)^2 = 73

Take the square root of both sides:
x - 4 = sqrt(73) or x - 4 = -sqrt(73)

Add 4 to both sides:
x = 4 + sqrt(73) or x - 4 = -sqrt(73)

Add 4 to both sides:

  x = 4 + sqrt(73) or x = 4 - sqrt(73) Thus the Answer is D: