Answer:
-4a²+4a³
Step-by-step explanation:
Answer: -32
You are taking away from "withdrawal"
Answer:
55
Step-by-step explanation:
The mean of n numbers is the sum of the numbers divided by n.
You have a mean score of 84 after taking 5 tests. Let x be the sum of scores.

You scored a total of 420 points on five tests.
You need to have a mean score of 85 after taking 6 tests. Let y be the score you need to obtain. Your total score on 6 tests is 420+y.

You need to score 90 points on the sixth test.