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Cubic equation roots

This is a bonus question I'm working on for an exam coming up.

Find the exact root of X^3 + X -1 = f(x). I need to find it in the format:

The exact root of X^2-x-1=0 is x=1+ or - the square root of 5 divided by 2. (Not a decimal or regular fractional number.)

I got all the others, but I just can't get this one. Thank you.

Solution Summary

This shows how to use Cardano's formula to find exact roots of a cubic equation.