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:
$$ \color{blue}{ b = 18 } ~ \text{ and } ~ \color{red}{ c = 56 }$$Now we must discover two numbers that sum up to $ \color{blue}{ 18 } $ and multiply to $ \color{red}{ 56 } $.
Step 2: Find out pairs of numbers with a product of $\color{red}{ c = 56 }$.
PRODUCT = 56 | |
1 56 | -1 -56 |
2 28 | -2 -28 |
4 14 | -4 -14 |
7 8 | -7 -8 |
Step 3: Find out which pair sums up to $\color{blue}{ b = 18 }$
PRODUCT = 56 and SUM = 18 | |
1 56 | -1 -56 |
2 28 | -2 -28 |
4 14 | -4 -14 |
7 8 | -7 -8 |
Step 4: Put 4 and 14 into placeholders to get factored form.
$$ \begin{aligned} x^{2}+18x+56 & = (x + \color{orangered}{\square} )(x + \color{orangered}{\square}) \\ x^{2}+18x+56 & = (x + 4)(x + 14) \end{aligned} $$