Answer:
The correct option is C.
Step-by-step explanation:
The given equation is

It can be rewritten as
.....(1)
The standard form of an ellipse is
....(2)
Where (h,k) is center of the ellipse.
If a>b, then the vertices of the ellipse are
.
From (1) and (2) we get

Since a>b, therefore the vertices of the ellipse are


The vertices of the given ellipse are (10, –7) and (2, –7). Therefore the correct option is C.
Answer:
0.02275
Step-by-step explanation:
We have been given that the time needed to complete a final examination in a particular college course is normally distributed with a mean of 80 minutes and a standard deviation of 10 minutes. We are asked to find the probability of completing the exam in one hour or less.
We know that 1 hour equals 60 minutes. First of all, we will find the z-score corresponding to 60 minutes.

z = z-score,
x = Sample score,
= Mean,
= Standard deviation.



Now, we will use normal distribution table to find area under z-score of
as:


Therefore, the probability of completing the exam in one hour or less is 0.02275.
Answer:
Use the normal distribution if the population standard deviation is known.
Use the student's t distribution when the population standard deviation is unknown.
Explanation:
A mound-shaped distribution refers to the normal distribution.
A good sample size for testing against the normal distribution should be
n >= 30.
The condition for the sample size is satisfied.
However, we are not given the population standard deviation, therefore it is assumed to be unknown.
Therefore the student's t distribution should be used.
1275 ÷ 9775= 0.1304% or 0.13%