A. The term "units" refers to the measurements in the original question or problem. When looking at the question, the units we are measuring are dollars/feet.
B. In this case, the f'(x) means we are looking for the cost (in dollars) to drill the next foot down.
C. Since the cost increases the more feet we drill down, the sign of f'(x) is positive.
Answer: Equilateral triangles are also right triangles sometimes. All angles of an equilateral are congruet sometimes.
Answer: 
Step-by-step explanation:
1. You must apply the following formula for calculate the total surface area the regular pyramid:

Where p is the perimeter of the base, l is the slant height and B is the area of the base.
2. The perimeter is, where s is the side length:

3. The faces are isosceles traingles. So, to find the slant height you can divide one base into two equal right triangles and calculate the slant height with Pythagorean Theorem:

4. The base is equal to any face, then both have equal areas. As previously you divide one base into two equal righ triangle to find the slant height, you can calcualte the area of one right triangle and multply it by 2 to calculate B:

Finally substitute values:

Answer:
$2,100
Step-by-step explanation:
In two weeks there is 14 days so, I times 150 by 14 which is 2100.
Complete Question
The complete question is shown on the first uploaded
Answer:
is not a solution of the differential equation
is not a solution of the differential equation
is not a solution of the differential equation
Step-by-step explanation:
The differential equation given is 
Let consider the first equation to substitute



So


So

This means that
is not a solution of the differential equation
Let consider the second equation to substitute



So

So

This means that
is not a solution of the differential equation
Let consider the third equation to substitute



So

So
This means that
is not a solution of the differential equation