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:
$$ \color{blue}{ b = 6 } ~ \text{ and } ~ \color{red}{ c = -16 }$$Now we must discover two numbers that sum up to $ \color{blue}{ 6 } $ and multiply to $ \color{red}{ -16 } $.
Step 2: Find out pairs of numbers with a product of $\color{red}{ c = -16 }$.
PRODUCT = -16 | |
-1 16 | 1 -16 |
-2 8 | 2 -8 |
-4 4 | 4 -4 |
Step 3: Find out which pair sums up to $\color{blue}{ b = 6 }$
PRODUCT = -16 and SUM = 6 | |
-1 16 | 1 -16 |
-2 8 | 2 -8 |
-4 4 | 4 -4 |
Step 4: Put -2 and 8 into placeholders to get factored form.
$$ \begin{aligned} x^{2}+6x-16 & = (x + \color{orangered}{\square} )(x + \color{orangered}{\square}) \\ x^{2}+6x-16 & = (x -2)(x + 8) \end{aligned} $$