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:
$$ \color{blue}{ b = 9 } ~ \text{ and } ~ \color{red}{ c = 8 }$$Now we must discover two numbers that sum up to $ \color{blue}{ 9 } $ and multiply to $ \color{red}{ 8 } $.
Step 2: Find out pairs of numbers with a product of $\color{red}{ c = 8 }$.
PRODUCT = 8 | |
1 8 | -1 -8 |
2 4 | -2 -4 |
Step 3: Find out which pair sums up to $\color{blue}{ b = 9 }$
PRODUCT = 8 and SUM = 9 | |
1 8 | -1 -8 |
2 4 | -2 -4 |
Step 4: Put 1 and 8 into placeholders to get factored form.
$$ \begin{aligned} y^{2}+9y+8 & = (x + \color{orangered}{\square} )(x + \color{orangered}{\square}) \\ y^{2}+9y+8 & = (x + 1)(x + 8) \end{aligned} $$