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:
$$ \color{blue}{ b = -9 } ~ \text{ and } ~ \color{red}{ c = 14 }$$Now we must discover two numbers that sum up to $ \color{blue}{ -9 } $ and multiply to $ \color{red}{ 14 } $.
Step 2: Find out pairs of numbers with a product of $\color{red}{ c = 14 }$.
PRODUCT = 14 | |
1 14 | -1 -14 |
2 7 | -2 -7 |
Step 3: Find out which pair sums up to $\color{blue}{ b = -9 }$
PRODUCT = 14 and SUM = -9 | |
1 14 | -1 -14 |
2 7 | -2 -7 |
Step 4: Put -2 and -7 into placeholders to get factored form.
$$ \begin{aligned} n^{2}-9n+14 & = (x + \color{orangered}{\square} )(x + \color{orangered}{\square}) \\ n^{2}-9n+14 & = (x -2)(x -7) \end{aligned} $$