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:
$$ \color{blue}{ b = -13 } ~ \text{ and } ~ \color{red}{ c = 30 }$$Now we must discover two numbers that sum up to $ \color{blue}{ -13 } $ and multiply to $ \color{red}{ 30 } $.
Step 2: Find out pairs of numbers with a product of $\color{red}{ c = 30 }$.
PRODUCT = 30 | |
1 30 | -1 -30 |
2 15 | -2 -15 |
3 10 | -3 -10 |
5 6 | -5 -6 |
Step 3: Find out which pair sums up to $\color{blue}{ b = -13 }$
PRODUCT = 30 and SUM = -13 | |
1 30 | -1 -30 |
2 15 | -2 -15 |
3 10 | -3 -10 |
5 6 | -5 -6 |
Step 4: Put -3 and -10 into placeholders to get factored form.
$$ \begin{aligned} p^{2}-13p+30 & = (x + \color{orangered}{\square} )(x + \color{orangered}{\square}) \\ p^{2}-13p+30 & = (x -3)(x -10) \end{aligned} $$