Step 1 :
After factoring out $ 4 $ we have:
$$ 4a^{2}-28a+48 = 4 ( a^{2}-7a+12 ) $$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:
$$ \color{blue}{ b = -7 } ~ \text{ and } ~ \color{red}{ c = 12 }$$Now we must discover two numbers that sum up to $ \color{blue}{ -7 } $ and multiply to $ \color{red}{ 12 } $.
Step 3: 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 4: 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 5: Put -3 and -4 into placeholders to get factored form.
$$ \begin{aligned} a^{2}-7a+12 & = (x + \color{orangered}{\square} )(x + \color{orangered}{\square}) \\ a^{2}-7a+12 & = (x -3)(x -4) \end{aligned} $$