Step 1 :
After factoring out $ 5 $ we have:
$$ 5x^{2}-100x+120 = 5 ( x^{2}-20x+24 ) $$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:
$$ \color{blue}{ b = -20 } ~ \text{ and } ~ \color{red}{ c = 24 }$$Now we must discover two numbers that sum up to $ \color{blue}{ -20 } $ and multiply to $ \color{red}{ 24 } $.
Step 3: Find out pairs of numbers with a product of $\color{red}{ c = 24 }$.
PRODUCT = 24 | |
1 24 | -1 -24 |
2 12 | -2 -12 |
3 8 | -3 -8 |
4 6 | -4 -6 |
Step 4: Because none of these pairs will give us a sum of $ \color{blue}{ -20 }$, we conclude the polynomial cannot be factored.