Step 1 :
After factoring out $ 5x $ we have:
$$ 5x^{3}+55x^{2}+150x = 5x ( x^{2}+11x+30 ) $$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:
$$ \color{blue}{ b = 11 } ~ \text{ and } ~ \color{red}{ c = 30 }$$Now we must discover two numbers that sum up to $ \color{blue}{ 11 } $ and multiply to $ \color{red}{ 30 } $.
Step 3: Find out pairs of numbers with a product of $\color{red}{ c = 30 }$.
PRODUCT = 30 | |
1 30 | -1 -30 |
2 15 | -2 -15 |
3 10 | -3 -10 |
5 6 | -5 -6 |
Step 4: Find out which pair sums up to $\color{blue}{ b = 11 }$
PRODUCT = 30 and SUM = 11 | |
1 30 | -1 -30 |
2 15 | -2 -15 |
3 10 | -3 -10 |
5 6 | -5 -6 |
Step 5: Put 5 and 6 into placeholders to get factored form.
$$ \begin{aligned} x^{2}+11x+30 & = (x + \color{orangered}{\square} )(x + \color{orangered}{\square}) \\ x^{2}+11x+30 & = (x + 5)(x + 6) \end{aligned} $$