# Homework Help: Solving for X (grph.calculator needed?)

1. Aug 22, 2011

### Wa1337

1. The problem statement, all variables and given/known data
Solve For x: x3 + 2x2 - 11x = 6

2. Relevant equations
N/A

3. The attempt at a solution
I got to x3 + 2x2 - 11x - 6 = 0

It says to list the windows I work with (using a graphing calculator). I am unable to since I don't have one and won't be assigned one until the school year starts. How do I go about solving this function for zeros.

2. Aug 22, 2011

### ArcanaNoir

This equation doesn't factor into whole numbers. :( Using the graphing calculator, you would graph it and then use the trace tool to find the roots. I believe there is a formula for cubic equations that is kind of like the quadratic equation but more complicated, but I don't know what it is.

3. Aug 22, 2011

### gb7nash

Try the rational root theorem:

http://en.wikipedia.org/wiki/Rational_root_theorem

If that doesn't work and you can't use iterative methods (which probably won't give you exact roots), it's cubic formula for you.

4. Aug 22, 2011

### Wa1337

Alright thank you. Will try and report back if I can :)

5. Aug 22, 2011

### I like Serena

I'm afraid the Rational root theorem doesn't work in this case.
And the formula for cubic equations is pretty messy:
http://en.wikipedia.org/wiki/Cubic_function

I'm afraid graphic calculator it is!