Step 1 :
After factoring out $ 3x $ we have:
$$ 3x^{3}-30x^{2}+27x = 3x ( x^{2}-10x+9 ) $$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:
$$ \color{blue}{ b = -10 } ~ \text{ and } ~ \color{red}{ c = 9 }$$Now we must discover two numbers that sum up to $ \color{blue}{ -10 } $ and multiply to $ \color{red}{ 9 } $.
Step 3: Find out pairs of numbers with a product of $\color{red}{ c = 9 }$.
PRODUCT = 9 | |
1 9 | -1 -9 |
3 3 | -3 -3 |
Step 4: Find out which pair sums up to $\color{blue}{ b = -10 }$
PRODUCT = 9 and SUM = -10 | |
1 9 | -1 -9 |
3 3 | -3 -3 |
Step 5: Put -1 and -9 into placeholders to get factored form.
$$ \begin{aligned} x^{2}-10x+9 & = (x + \color{orangered}{\square} )(x + \color{orangered}{\square}) \\ x^{2}-10x+9 & = (x -1)(x -9) \end{aligned} $$