It seems that $ -x^{2}-3x-18 $ cannot be factored out.
Step 1 :
After factoring out $ -1 $ we have:
$$ -x^{2}-3x-18 = - ~ ( x^{2}+3x+18 ) $$Step 2 :
Step 2: 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:
$$ \color{blue}{ b = 3 } ~ \text{ and } ~ \color{red}{ c = 18 }$$Now we must discover two numbers that sum up to $ \color{blue}{ 3 } $ and multiply to $ \color{red}{ 18 } $.
Step 3: Find out pairs of numbers with a product of $\color{red}{ c = 18 }$.
PRODUCT = 18 | |
1 18 | -1 -18 |
2 9 | -2 -9 |
3 6 | -3 -6 |
Step 4: Because none of these pairs will give us a sum of $ \color{blue}{ 3 }$, we conclude the polynomial cannot be factored.