Solve for x:
x^3 - 7 x^2 - 12 x + 54 = 0
The left hand side factors into a product with two terms:
(x + 3) (x^2 - 10 x + 18) = 0
Split into two equations:
x + 3 = 0 or x^2 - 10 x + 18 = 0
Subtract 3 from both sides:
x = -3 or x^2 - 10 x + 18 = 0
Subtract 18 from both sides:
x = -3 or x^2 - 10 x = -18
Add 25 to both sides:
x = -3 or x^2 - 10 x + 25 = 7
Write the left hand side as a square:
x = -3 or (x - 5)^2 = 7
Take the square root of both sides:
x = -3 or x - 5 = sqrt(7) or x - 5 = -sqrt(7)
Add 5 to both sides:
x = -3 or x = 5 + sqrt(7) or x - 5 = -sqrt(7)
Add 5 to both sides:
Answer: | x = -3 or x = 5 + sqrt(7) or x = 5 - sqrt(7)