Question

what is the factored form of $x^2 - 4x - 5$?\
\bigcirc $(x + 5)(x - 1)$\
\bigcirc $(x + 5)(x + 1)$\
\bigcirc $(x - 5)(x - 1)$\
\bigcirc $(x - 5)(x + 1)$

Explanation:

Step1: Find pair of factors for -5

We need two numbers that multiply to $-5$ and add to $-4$. The numbers are $-5$ and $1$, since $(-5)\times1=-5$ and $-5+1=-4$.

Step2: Write factored form

Using the two numbers, the quadratic factors as $(x + \text{first number})(x + \text{second number})$.

Answer:

D. $(x - 5)(x + 1)$