Question #00168

1 Answer
Oct 13, 2015

You may have copied the problem down incorrectly, because the exact roots are not pleasant to write down. The three roots are approximately #3.62793#, #-0.113965 pm 0.90218i#, where #i=sqrt(-1)#.

Explanation:

There is a method to solve cubics exactly. You can find it here: formula for roots of cubic

If you are "lucky" and the cubic has rational number roots, the rational root theorem can be used to find exact answers.

Your example has no rational roots. Here's a screenshot of what Wolfram Alpha produces for the exact answers:

enter image source here