Answer:
Let p(x)=x
3
−4x
2
−2x+20
By factor theorem, (x+2) is a factor of p(x) if p(−2)=0.
∴ It is sufficient to show that (x+2) is a factor of p(x)
Now, p(x)=x
3
−4x
2
−2x+20
∴p(−2)=(−2)
3
−4(−2)
2
−2(−2)+20=−8−16+4+20=0
∴(x+2) is a factor of p(x)=x
3
−4x
2
−2x+20