Answer:
n = 20 or n = -2
Explanation:
Solve for n over the real numbers:
n^2 = 18 n + 40
Subtract 18 n + 40 from both sides:
n^2 - 18 n - 40 = 0
The left hand side factors into a product with two terms:
(n - 20) (n + 2) = 0
Split into two equations:
n - 20 = 0 or n + 2 = 0
Add 20 to both sides:
n = 20 or n + 2 = 0
Subtract 2 from both sides:
Answer: n = 20 or n = -2