Step 1 :
After factoring out $ 4 $ we have:
$$ 4x^{2}+20x+24 = 4 ( x^{2}+5x+6 ) $$Step 2 :
Step 2: 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:
$$ \color{blue}{ b = 5 } ~ \text{ and } ~ \color{red}{ c = 6 }$$Now we must discover two numbers that sum up to $ \color{blue}{ 5 } $ and multiply to $ \color{red}{ 6 } $.
Step 3: Find out pairs of numbers with a product of $\color{red}{ c = 6 }$.
PRODUCT = 6 | |
1 6 | -1 -6 |
2 3 | -2 -3 |
Step 4: Find out which pair sums up to $\color{blue}{ b = 5 }$
PRODUCT = 6 and SUM = 5 | |
1 6 | -1 -6 |
2 3 | -2 -3 |
Step 5: Put 2 and 3 into placeholders to get factored form.
$$ \begin{aligned} x^{2}+5x+6 & = (x + \color{orangered}{\square} )(x + \color{orangered}{\square}) \\ x^{2}+5x+6 & = (x + 2)(x + 3) \end{aligned} $$