Can you please help me on this??

Use sigma notation to represent the following series for 9 terms.

Hi i’m not sure how to do question 20 if u could explain how to do it that’d b great

Sanderson is having trouble with his assignment. his shown work is as follows: − 3 7 7 3 = − 3 7 × 7 3 = − 21 21 = −1 however, his answer does not match the answer that his teacher gives him. complete the description of sanderson's mistake. find the correct answer.