Question

Help please! Finals tomorrow! I need help with factoring. x^3-x^2-9x+18

Answer 1

you gotta take a guess, like guess an x that might work
good guesses can be made by look at the coefficients of x^3 and the constant term

Answer 2

you guess +/- the factors of the coeffecient on X^3 or the constant in the end

Answer 3

so like +/-1 or +/-2 or +/-3 or +/-6 and so on one of those will work for sure if they expect this to be factored

Answer 4

guess that and then say +3 worked
then you would do synthetic division with (x+3)

Answer 5

this does not have good factors wuut

Answer 6

you are going to have to use stuff like newtons method to get a real close approximation

Answer 7

http://www.wolframalpha.com/input/?i=x%5E3-x%5E2-9x%2B18%3D0

Answer 8

As far as factoring goes, the best you can do is this:

\(x^3 - x^2 - 9x + 18 = x^2(x - 1) - 9(x - 2)\)
\(= x^2(x - 1) - 9(x - 1) + 9\)
\(= (x - 1)(x^2 - 9) + 9\)
\(= (x - 1)(x + 3)(x - 3) + 9\)

In the end, you'll have 9 left over no matter what you do