Factor polynomial $$ 5x^{3}+15x^{2}-20x $$

$$ 5x^{3}+15x^{2}-20x = 5x( x-1 )( x+4 ) $$

Step 1 :

After factoring out $ 5x $ we have:

$$ 5x^{3}+15x^{2}-20x = 5x ( x^{2}+3x-4 ) $$

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:

$$ \color{blue}{ b = 3 } ~ \text{ and } ~ \color{red}{ c = -4 }$$

Now we must discover two numbers that sum up to $ \color{blue}{ 3 } $ and multiply to $ \color{red}{ -4 } $.

Step 3: Find out pairs of numbers with a product of $\color{red}{ c = -4 }$.

PRODUCT = -4
-1     4	1     -4
-2     2	2     -2

Step 4: Find out which pair sums up to $\color{blue}{ b = 3 }$

PRODUCT = -4 and SUM = 3
-1     4	1     -4
-2     2	2     -2

Step 5: Put -1 and 4 into placeholders to get factored form.

$$ \begin{aligned} x^{2}+3x-4 & = (x + \color{orangered}{\square} )(x + \color{orangered}{\square}) \\ x^{2}+3x-4 & = (x -1)(x + 4) \end{aligned} $$

Polynomial Factoring Calculator