Roots of a polynomial (simple!)

1. Jul 16, 2008

camilus

$$x^3-7x^2-10x-8 = 0$$

what are the roots?? Sorry, Im horrible at doing these kinds of things, this is for another problem in my differential equations thread.

Its been so long since I did simple roots of a polynomial, I forgot how to do it LOL! and please, this homework is due tomorrow morning, so if you can help please spare the lesson until tomorrow afternoon. I need this done by tonight, preferably right now. Thanks!

2. Jul 16, 2008

epkid08

Use p/q method to factor.

3. Jul 16, 2008

camilus

elaborate please! I havent done simple algebra like this in like 2-3 years!

I was thinking synthetic division. Would that work?

4. Jul 16, 2008

camilus

Jesus Christ!!! I had the wrong polynomial!!

this is the right one.

$$x^3-7x^2+6x-8 = 0$$

5. Jul 16, 2008

rock.freak667

You'd probably need to look for that formula to find the roots of a cubic polynomial since I believe that doesn't have rational roots.

6. Jul 16, 2008

camilus

yeah, 2 roots are imaginary, and 1 root is real.

The three roots are according to my calculator, 6.244297529863042, 0.37785123506847906 + i* 1.06695706407035, and 0.37785123506847906 - i* 1.06695706407035.

But theres gotta be a nicer way of writing that...

7. Jul 16, 2008

rock.freak667

Check here and see if you can write it in a better way.