Answer:
x = 12 or x = -3
Step-by-step explanation:
Solve for x over the real numbers:
x^2 - 9 x = 36
Subtract 36 from both sides:
x^2 - 9 x - 36 = 0
x = (9 ± sqrt((-9)^2 - 4 (-36)))/2 = (9 ± sqrt(81 + 144))/2 = (9 ± sqrt(225))/2:
x = (9 + sqrt(225))/2 or x = (9 - sqrt(225))/2
sqrt(225) = sqrt(9×25) = sqrt(3^2×5^2) = 3×5 = 15:
x = (9 + 15)/2 or x = (9 - 15)/2
(9 + 15)/2 = 24/2 = 12:
x = 12 or x = (9 - 15)/2
(9 - 15)/2 = -6/2 = -3:
Answer: x = 12 or x = -3
