quadratic equation: how to solve x^3 -15x + 15

[Motherof8]

How would you solve this equation? x^3 -15x + 15. When I say (x^2 -15) (x -1) I end up with an extra -x ^2.

[nona.m.nona]

How would you solve this equation? x^3 -15x + 15.

Since the degree of the leading term is 3, this is therefore a cubic, and not a quadratic, expression.

To solve (by which I assume you mean finding the zeroes), one would customarily use the methodology outlined in this article. However, that methodology will fail due to the fact that this expression has no rational zeroes. Therefore, one would need to use numerical methods to approximate the zeroes.