]1. The problem statement, all variables and given/known data Solving the cubic equation x^3 + 6x = 20 by using formula gives (10+ sqrt(108))^1/3 - (-10 + sqrt(108))^1/3 How do you show that this comes out exactly 2? No calculators allowed. 2. Relevant equations 3. The attempt at a solution Tried cubing the expression and tried using the Difference of Cubes formula.