Question

What is the factored form of x2 − 4x − 5?

(x + 5)(x − 1)

(x + 5)(x + 1)

(x − 5)(x − 1)

(x − 5)(x + 1)

Answer 1

Factors of -5 are -5 and 1 or 5 and -1

-5 + 1 = -4 so D is the correct answer.

Answer 2

(x - 5)(x + 1)

Explanation:

To solve this, using knowledge of quadratic equations, the two numeral elements (the x intercepts) of the factors, would be a form of 1 and 5, as when they are multiplied by one another they will produce a 5 and when 1 is subtracted from 5 it gives a difference of 4. To get - 4, the 5 has to be negative. The results can be tested by multiplying out the two brackets.

`(x-5)(x+1)\\=x^(2)-5x+1x-5\\=x^(2) -4x-5`