Can someone please help me? I am trying to explain this to my son but I am in way over my head with this problem. Would someone be so kind as to give me a step by step?

A student used synthetic division to divide x^3-x^2-2x by x+1 .
This is what the students problem looked like
1) 1 -1 -2
1 0
____________
1 0 -2
answer x remainder -2
a. Describe and correct the error shown.
b. Use the Remainder theorem to double check the remainder you found in part a.

see thishttps://www.jiskha.com/questions/1809234/A-student-used-synthetic-division-to-divide-x-3-x-2-2x-by-x-1-This-is-what-the