Using the factor Theorem
posted by Rose .
use the factor theorem to determine whether xc is a factor of f(x)
f(x)=x^3+8x^218x+20; x10
I have a doubt in my answer, i determined that x10 is not a factor... am i right? please verify as my exam is tomorrow night at college. thank you for your time and hard work:)

It can be shown that x10 is not a factor of x^3+8x^218x+20. So your are correct.
If you wish, you could try (x+10) and show that it is a factor of x^3+8x^218x+20. 
thank you so much dear mate, yes i took your advise and indeed i got it as a factor:) thank you.

You're welcome!