Because they make 4 dollars for every book sold, a representative equation would be:
Using the t-distribution, it is found that the test statistic for the hypotheses test is given by:

<h3>What are the hypotheses tested?</h3>
At the null hypotheses, it i tested if the mean difference remains the same, that is:

At the alternative hypotheses, it is tested if it has decreased, hence:
.
<h3>What is the test statistic?</h3>
The test statistic is given by:

The parameters are:
is the sample mean.
is the value tested at the null hypothesis.
- s is the standard deviation of the sample.
The parameters are given as follows:
.
Hence the test statistic is given by:


More can be learned about the t-distribution at brainly.com/question/16162795
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Answer:
B. 
Step-by-step explanation:
![\displaystyle x^2 = -8x - 7 → x^2 + 8x + 7 \\ \\ x^2 + 8x + 7 \\ [x + 1][x + 7]; -1, -7 = x](https://tex.z-dn.net/?f=%5Cdisplaystyle%20x%5E2%20%3D%20-8x%20-%207%20%E2%86%92%20x%5E2%20%2B%208x%20%2B%207%20%5C%5C%20%5C%5C%20x%5E2%20%2B%208x%20%2B%207%20%5C%5C%20%5Bx%20%2B%201%5D%5Bx%20%2B%207%5D%3B%20-1%2C%20-7%20%3D%20x)
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Answer:
81/4
Step-by-step explanation:
I know this because I did this before