Answer:
See below.
Step-by-step explanation:
First, notice that this is a composition of functions. For instance, let's let and
. Then, the given equation is essentially
. Thus, we can use the chain rule.
Recall the chain rule: . So, let's find the derivative of each function:
We can use the Power Rule here:
Now:
Again, use the Power Rule and Sum Rule
Now, we can put them together:
So we know that an average is the sum of the scores divided by the number of scores that were added together. In this case we are going to be dealing with 4 tests. So let's say x is the score for our fourth test. We can create this equation:
So then we need to simplify the top:
Then multiply by 4 on both sides to get rid of the denominator:
Then solve for x:
So now we know that Sam needs to score a 67 on the fourth test to have an average score of 50.