In this question, you're trying to find the unit rate in which the teacher can grade tests.
A unit rate is another word for "rate of change".
This means that we have to find how many tests the teacher could grade in 1 minute.
To find the unit rate, divide 18 by 15
18 ÷ 15 = 1.2
This means that Mr. Rivera can grade 1.2 tests in 1 minute.
Answer:
1.2 tests
From the description, we have the function

Since the square root cannot be a negative number, the only thing need to do to find the domain of the function

is take the expression inside the square rot and set it greater or equal than zero:




or

We can conclude that we can use the inequality

to find the domain of

. Also, the domain of

is (∞,

]U(5,∞).
Answer: Zero; 9; -18
Step-by-step explanation:
An additive inverse always adds up to zero. 9 is the opposite of -9, and -18 is the opposite of 18