Question

Factor: 5x2 – 15x – 20

(a) 5(x-4)(x+1)

(b) -2(x-4)(x+5)

(c) -5(x+4)(x-1)

(d) 5(x+4)(x+1)

Answer 1

A.

Explanation:

5x^2 – 15x – 20

= 5(x^2 – 3x – 4)

= 5(x^2 – 4x + x – 4)

= 5{x(x - 4) +1(x - 4)}

= 5(x-4)(x+1)