Factor: 5x2 – 15x – 20. Choose the correct answer:
A) 5(x-4)(x+1) B) -2(x-4)(x+5) C) -5(x+4)(x-1) D) 5(x+4)(x+1) E) 6(x+4)(x+1)
Solution:   5x2 – 15x – 20.   = 5(x2 – 3x – 4).   = 5(x2 – 4x + x – 4).   = 5{x(x - 4) +1(x - 4)}.   = 5(x-4)(x+1).   5(x-4)(x+1)nswer: (5(x-4)(x+1)).
<result>A</result>
Factor: 5x2 – 15x – 20.