How do I factor polynomials?

Question

I don't understand how to factor this polynomial:

 

x^2-x-20

Answer 1

You want to look at the expession and see if there are any numbers or variable that can be factored out. 

Set up the formula: .

x^2-#x-#

Find factors of twenty:10×2, 5×4, 20×1. 

 

We know that the factors have to be able to come together to make -1 (because we had -x). 5-4=1, 4-5=-1. There for we have +4 and -5.

(x+#)(x-#)

(x+4)(x-5)

Answer 2

x² - x - 20

 

What are two numbers whose product is 20 and sum/difference is 1?

 

(x - 5)(x + 4)