Showing posts with label Factoring Polynomials. Show all posts
Showing posts with label Factoring Polynomials. Show all posts

Friday, April 4, 2014

x^3 - 5x^2 +8x-4=0 Answer is 1 or 2 but having difficulty figuring out how to solve this other than trial and error.

We could use DesCartes rule of signs, to show 3 positive roots, then the rational zeros test to narrow the choices. Finally using synthetic division to get them. However, since we know them and they are rational, let's factor.

x%5E3+-+5x%5E2+%2B8x-4=%28x%5E3-4x%5E2%2B4x%29-%28x%5E2-4x%2B4%29
Then...
x%28x%5E2-4x%2B4%29-1%28x%5E2-4x%2B4%29=%28x-1%29%28x-2%29%5E2

Tuesday, January 28, 2014

What are the rational routes of 8x^3+2x^2-5x+1=0 ?

By using synthetic division we can write:
8x^3+2x^2-5x+1=(x+1)(8x^2-6x+1)
then by the quadratic equation, factoring, or some other method we get
8x^3+2x^2-5x+1=(x+1)(2x-1)(4x-1)
The roots are: {-1, 1/2 1/4}

Saturday, December 7, 2013

Saturday, November 30, 2013

Factorize m^4+m^2+1

Factoring isn't easy, until you get good at it. One useful technique is to introduce terms that add to 0 as follows:

m%5E4%2Bm%5E2%2B1=m%5E4-m%5E3%2Bm%5E3%2Bm%5E2%2B1

m%5E4-m%5E3%2Bm%5E3%2Bm%5E2%2B1=%28m%5E4%2Bm%5E3%2Bm%5E2%29%2B%281-m%5E3%29
now we can write...

rearranging and grouping leads to
%28m%5E2%2Bm%2B1%29%28m%5E2-m%2B1%29

Saturday, August 31, 2013

find the zeros fro g(x), g(x) = 4(x + 2)^5 (x-3)^3 + 5(x-3)^4 (x+2)^4

by grouping 
4%28x+%2B+2%29%5E5+%28x-3%29%5E3+%2B+5%28x-3%29%5E4+%28x%2B2%29%5E4 
becomes 
%28x%2B2%29%5E4%28x-3%29%5E3%284%28x%2B2%29%2B5%28x-3%29%29 

which simplifies to 
%28x%2B2%29%5E4%28x-3%29%5E3%289x-7%29 
so there are 3 unique solutions: 
x=-2 (multiplicity 4)
x=3 (multiplicity 3)
x=7/9

Sunday, May 19, 2013