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1 year ago in Algebra , Numerical Analysis By Shilpa A

Is there a general formula to determine cube roots of non-perfect cubes?

While teaching numerical methods, students often ask if they missed a simple formula like the quadratic formula for cube roots. I know perfect cubes are trivial and iterative methods work, but I want to confirm the deeper mathematical truth: is a general, exact algebraic formula impossible, or just not commonly taught?

 

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By Rinku Answered 1 year ago

The short, critical answer is no there is no general algebraic formula (using only radicals and elementary operations) for the cube roots of arbitrary integers or non-perfect cubes. This is rooted in Galois theory; solving the equation x³ - N = 0 generally falls into territory where solutions cannot be neatly expressed by radicals alone. In practice, I always recommend methods like Newton-Raphson. They converge rapidly and are far more practical than seeking a non-existent "simple" formula.

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