Factor polynomial $$ x^{2}-3x-4 $$

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

Step 1: 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 2: Find out pairs of numbers with a product of $\color{red}{ c = -4 }$.

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

Step 3: 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 4: 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