If x2 - 6x - 40 = (x + 4)(x + a) then the value of a is:
-10
5
10
-5
x2 - 6x - 40
= x2 - 10x + 4x - 40
= x(x - 10) + 4(x - 10)
= (x + 4)(x - 10)
Thus, a = 4 OR a = -10