Thinking back on your math classes, you may recall that the square root of a number has two answers, one positive and one negative. For example, the square root of +9 is both +3 and -3 (the first one is known as the principal square root). Squaring +3 gives you +9, of course, but so does squaring -3.

Square roots aren’t the only roots of a number. For example, the (principal) cube root of +8 is +2 because +2³ =  +2 × +2 × +2 = +8.

But just as square roots have two answers, cube roots have three (and fourth roots have four and so on and so on).

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