hmmm I'd do synthetic division here.
you set it up as
n | coefficient of first, second, third,...so on|
where n is from x-n, a factor of my polynomial. I realize that's a bad explanation so I'll show it with this one
so, setting this up, I have x-8 as my potential factor, so n would equal 8.
8 |
now list the coefficients of all the terms in your polynomial.
8 | 1... -3.... -31.... -72 |
you drop down the first coefficient shown, and multiply it by n, and put that under the second coeffiecient, then add.
8 | 1 ...-3 ....-31 ....-72|
......1 ..+ 8 (1)
8 + -3 is 5, so multiply 5 by 8 and put that under the next coeffient, add, and so on.
8 | 1 ......-3..... -31..... -72|
......1 .....+ 8... +40 ...+72
...............5 ........9........ 0
if I get a remainder of 0, or a 0 after you've done everything (which we have) then whatever x-n you have IS a factor of your polynomial. so, x-8 is a fsctor. :) hope that helps!
EDIT: sorry about the periods haha. just trying to make it easier to see.