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:
$$ \color{blue}{ b = 7 } ~ \text{ and } ~ \color{red}{ c = 12 }$$Now we must discover two numbers that sum up to $ \color{blue}{ 7 } $ and multiply to $ \color{red}{ 12 } $.
Step 2: 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 3: Find out which pair sums up to $\color{blue}{ b = 7 }$
PRODUCT = 12 and SUM = 7 | |
1 12 | -1 -12 |
2 6 | -2 -6 |
3 4 | -3 -4 |
Step 4: Put 3 and 4 into placeholders to get factored form.
$$ \begin{aligned} x^{2}+7x+12 & = (x + \color{orangered}{\square} )(x + \color{orangered}{\square}) \\ x^{2}+7x+12 & = (x + 3)(x + 4) \end{aligned} $$