It seems that $ x^{2}+9x-20 $ 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:
$$ \color{blue}{ b = 9 } ~ \text{ and } ~ \color{red}{ c = -20 }$$Now we must discover two numbers that sum up to $ \color{blue}{ 9 } $ and multiply to $ \color{red}{ -20 } $.
Step 2: Find out pairs of numbers with a product of $\color{red}{ c = -20 }$.
PRODUCT = -20 | |
-1 20 | 1 -20 |
-2 10 | 2 -10 |
-4 5 | 4 -5 |
Step 3: Because none of these pairs will give us a sum of $ \color{blue}{ 9 }$, we conclude the polynomial cannot be factored.