Posted by **Amelie** on Sunday, December 2, 2007 at 4:37pm.

I'm having a hard time factoring polynomials, especially 3rd degree.

-x^3+2x^2+4x-8

-x^3-5x^2+20x+12

I don't know how to begin. I thought long division, but what would I divide by?

- Math: Factoring -
**drwls**, Sunday, December 2, 2007 at 5:03pm
First find one root by trial and error. Call it a. Then divide (x-a) into the cubic using long division to get a quadratic equation. Get the roots of that by the usual method.

For the equation

-x^3+2x^2+4x-8,

one of the roots is x=2. Divide (x-2) into -x^3+2x^2+4x-8, and you get

-x^2 + 4 = (4-2)(x+2)

That completes the factoring.

-x^3+2x^2+4x-8 = (x-2)(x+2)(2-x)

## Answer this Question

## Related Questions

- Advanced Algebra - Divide using long division or synthetic division. (21x^3 - 7...
- Long/synthetic divison - Divide using long division or synthetic division. (21x^...
- Factoring- precalc - im stuck on factoring (x-1)(2x^3+13x^2+8x-35) do i use ...
- Precalc factoring - im stuck on factoring (x-1)(2x^3+13x^2+8x-35) do i use ...
- Math-Factoring - Hey I need help factoring 5x^4-180x^2. I'm used to factoring ...
- math - i am having a hard time with factoring i have read what is here but am ...
- Factoring - x2(squared)-4x+4 I would factor this into (X - 2)(X - 2) If you don'...
- Algebra 2 - I am trying to factor a 4th degree polynomial that does not have any...
- lisa - This is a question given to me to answer:How is dividing a polynomial by ...
- Algebra: factoring - I need to find the value of x. 9x^3 + 9x = 30x^2 It's ...

More Related Questions