It seems that $ x^{2}+20x-80 $ cannot be factored out.
Step 1: Identify constants $ \color{blue}{ b }$ and $\color{red}{ c }$. ( $ \color{blue}{ b }$ is a number in front of the $ x $ term and $ \color{red}{ c } $ is a constant). In our case:
$$ \color{blue}{ b = 20 } ~ \text{ and } ~ \color{red}{ c = -80 }$$Now we must discover two numbers that sum up to $ \color{blue}{ 20 } $ and multiply to $ \color{red}{ -80 } $.
Step 2: Find out pairs of numbers with a product of $\color{red}{ c = -80 }$.
PRODUCT = -80 | |
-1 80 | 1 -80 |
-2 40 | 2 -40 |
-4 20 | 4 -20 |
-5 16 | 5 -16 |
-8 10 | 8 -10 |
Step 3: Because none of these pairs will give us a sum of $ \color{blue}{ 20 }$, we conclude the polynomial cannot be factored.