Question

a3-21a_20 middle factor​

Answer 1

Answer:

a^3 - 21a - 20 = a^3 -a -20a -20 =

(a^3-a) -(20a + 20)=a (a^2 - 1) - 20(a+1) = a(a+1)(a-1)-

20(a+1)

(a+1){a(a-1) -20}=

(a+1)(a^2 -a - 20)

(a+1) {a^2 -5a +4a -20}=

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