Step 1 :
After factoring out $ n $ we have:
$$ n^{3}-9n^{2}-1000n = n ( n^{2}-9n-1000 ) $$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:
$$ \color{blue}{ b = -9 } ~ \text{ and } ~ \color{red}{ c = -1000 }$$Now we must discover two numbers that sum up to $ \color{blue}{ -9 } $ and multiply to $ \color{red}{ -1000 } $.
Step 3: Find out pairs of numbers with a product of $\color{red}{ c = -1000 }$.
PRODUCT = -1000 | |
-1 1000 | 1 -1000 |
-2 500 | 2 -500 |
-4 250 | 4 -250 |
-5 200 | 5 -200 |
-8 125 | 8 -125 |
-10 100 | 10 -100 |
-20 50 | 20 -50 |
-25 40 | 25 -40 |
Step 4: Because none of these pairs will give us a sum of $ \color{blue}{ -9 }$, we conclude the polynomial cannot be factored.