# Finding zeros of a polynominal that doesn't factor (and whose zeros are non-integers)

• Mar 26th 2013, 03:03 PM
ncpenn
Finding zeros of a polynominal that doesn't factor (and whose zeros are non-integers)
I've got this here . . . x^3 +7x -1 = 0.

I know it equals x = 0.142 approx, but I found that out by graphing it. I'm stumped as to how to solve it algebraically. (Headbang)

Any help is much appreciated.

Thanks!
• Mar 26th 2013, 03:49 PM
Bean
Re: Finding zeros of a polynominal that doesn't factor (and whose zeros are non-integ
Wikipedia has a pretty comprehensive article regarding how to solve a cubic algebraically.

Cubic function - Wikipedia, the free encyclopedia
• Mar 26th 2013, 05:20 PM
Prove It
Re: Finding zeros of a polynominal that doesn't factor (and whose zeros are non-integ
You should use a numerical method. Otherwise use the Cubic Formula if you really feel adventurous...
• Mar 27th 2013, 09:50 AM
joeDIT
Re: Finding zeros of a polynominal that doesn't factor (and whose zeros are non-integ
Yea I'd go with what Prove it said above and that wiki article should help alot. if it helps at all your looking for 3 roots and two of them are complex roots.