Question

question
factor.
$x^2 - 3x - 4$
answer attempt 1 out of 2

Explanation:

Step1: Find pair for product -4, sum -3

We need two numbers that multiply to $-4$ and add to $-3$. These numbers are $-4$ and $1$, since $(-4)\times1=-4$ and $(-4)+1=-3$.

Step2: Split middle term and factor

Rewrite the quadratic using the pair, then factor by grouping:

$$\begin{align*} x^2 - 3x - 4&=x^2 - 4x + x - 4\\ &=x(x-4)+1(x-4)\\ &=(x-4)(x+1) \end{align*}$$

Answer:

$(x-4)(x+1)$