Cube root
In mathematics, a cube root of a number x is a number such that a3 = x. All real numbers (except zero) have exactly one real cube root and a pair of complex conjugate cube roots, and all nonzero complex numbers have three distinct complex cube roots. For example, the real cube root of 8, denoted 3√8, is 2, because 23 = 8, while the other cube roots of 8 are −1 + √3i and −1 − √3i. The three cube roots of −27i are
The cube root operation is not associative or distributive with addition or subtraction.
In some contexts, particularly when the number whose cube root is to be taken is a real number, one of the cube roots (in this particular case the real one) is referred to as the principal cube root, denoted with the radical sign 3√. The cube root operation is associative with exponentiation and distributive with multiplication and division if considering only real numbers, but not always if considering complex numbers: for example, the cube of any cube root of 8 is 8, but the three cube roots of 83 are 8, −4 + 4i√3, and −4 − 4i√3.
The cube roots of a number x are the numbers y which satisfy the equation
For any real number y, there is one real number x such that x3 = y. The cube function is increasing, so does not give the same result for two different inputs, plus it covers all real numbers. In other words, it is a bijection, or one-to-one. Then we can define an inverse function that is also one-to-one. For real numbers, we can define a unique cube root of all real numbers. If this definition is used, the cube root of a negative number is a negative number.
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