solve Polynominal question - easy

• Jul 20th 2009, 03:04 AM
Awsom Guy
solve Polynominal question - easy
X^3-1/X+2

This says X to the power of 3, subtract 1, divided by, X plus 2.
Thanks I coudn't even start this question because all the other question had three or more top numbers like X^3+2X^2-13X+10.
I need this help.
Thanks for the help....(Nod)
• Jul 20th 2009, 03:11 AM
mr fantastic
Quote:

Originally Posted by Awsom Guy
X^3-1/X+2

This says X to the power of 3, subtract 1, divided by, X plus 2.
Thanks I coudn't even start this question because all the other question had three or more top numbers like X^3+2X^2-13X+10.
I need this help.
Thanks for the help....(Nod)

What are you meant to be doing with this expression? Please post the question exactly as it's written in wherever you got it from.
• Jul 22nd 2009, 04:36 PM
kanu999
Hi

Well are you trying to solve for X when that equation is equal to ZERO?

e.g. ((X^3)-1)/(X+2) = 0

If so then all you need to do is solve for (X^3)-1 = 0, because if the top line is zero then the whole fraction is zero.

Therefore solving that equation will give an answer of X=1.

Also there are two more solutions (it is a cubic).In order to get those you need to do long division on (X^3)-1 with (X-1), which will then give an equation of ((X^2)-X+1). And when you solve this for zero you will get two complex roots 0.5+0.86i and 0.5-0.86i

Hope this helps
• Jul 23rd 2009, 12:49 AM
Opalg
Quote:

Originally Posted by Awsom Guy
X^3-1/X+2

This says X to the power of 3, subtract 1, divided by, X plus 2.
Thanks I coudn't even start this question because all the other question had three or more top numbers like X^3+2X^2-13X+10.

If this is a question about how to do polynomial division, you should think of the numerator as being $x^3 + 0x^2 + 0x - 1$. Then it will have "three or more top numbers" (even though some of them are zero), and you can divide it by x+2 in just the same way as you would if it was something like " $X^3+2X^2-13X+10$".