Answer:
a=0
Solution,
To find a,
We should know that,
Factor of polynomial gives root of polynomial like:x-a if a factor of p(X) then p(a)=0 at X=a
So,
X+1=0
X=0-1
X=-1
put x=-1 into p(X) it gives zero.
hope this helps....
Good luck on your assignment....