The principal nth root is the non-negative root when n is even and a ≥ 0. Even roots of negatives are not real. Odd roots allow negative radicands. Verify by raising the root back to n.
Variables
aradicand
nroot index (2 = square root, 3 = cube root, …)
bthe root
When to use
Geometry (side from area/volume), RMS-style calculations, and undoing powers.