Step 1 :
After factoring out $ 6 $ we have:
$$ 6x^{2}-18x-72 = 6 ( x^{2}-3x-12 ) $$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:
$$ \color{blue}{ b = -3 } ~ \text{ and } ~ \color{red}{ c = -12 }$$Now we must discover two numbers that sum up to $ \color{blue}{ -3 } $ and multiply to $ \color{red}{ -12 } $.
Step 3: Find out pairs of numbers with a product of $\color{red}{ c = -12 }$.
PRODUCT = -12 | |
-1 12 | 1 -12 |
-2 6 | 2 -6 |
-3 4 | 3 -4 |
Step 4: Because none of these pairs will give us a sum of $ \color{blue}{ -3 }$, we conclude the polynomial cannot be factored.