Answer:
Only C is a function
Step-by-step explanation:
To test whether a graph is a function you use the vertical line test.
If you can place a vertical line anywhere on the plane (in the domain of the "function" to be tested) and it intersects the curve at more than one point, the curve is not a function.
We see with A, wherever we put the vertical line it intersects twice.
With B, it intersects infinitely many times.
C is a function because wherever we put the vertical line, it only intersects once.
D is a function because it intersects twice providing we do not put it on the "tip" of the parabola.
The mathematical reasoning behind this is that a function must be well-defined, that is it must send every x-value to one specific y-value. There can be no confusion about where the function's input is going. If you look at graph B and I ask you what is f(3)? Is it 1? 2? 3? ... Who knows, it's not well-defined and so it's not a function. However if I ask you about C, whichever input value for x I give you, you can tell me to which y-value it gets mapped/sent to.
First, let

be a point in our parabola. Since we know that the focus of our parabola is the point (0,8), we are going to use the distance formula to find the distance between the two points:

Next, we are going to find the distance between the directrix and the point in our parabola. Remember that the distance between a point (x,y) of a parabola and its directrix,

, is:

. Since our directrix is y=-8, the distance to our point will be:


Now, we are going to equate those two distances, and square them to get rid of the square root and the absolute value:



Finally, we can expand and solve for

:




We can conclude that t<span>he standard form of the equation of the parabola with a focus at (0, 8) and a directrix at y = -8 is </span>
First we need to know how many months is 2 years. To answer that we multiply the number of months in a year by 2 and get 48 months.
Every 3 months the population of turtles doubles, but to get how many times the population doubles, you need to divide 48 months by 3 to get 16.
So population of 400 will get <u>doubled</u> 16 times in the following <u>two</u> years.
We construct the following equation where
is the final population,

Hope this helps. :)
This problem is fairly simple if you know the exponential equation, you start with y=78(.17)^x. the you put 10=78(.17)^x, then you solve for x
10=78(.17)^x
-78
-68=.17^x
divide .17 then you have your answer!!
X^4 + x^3 + x^2 + x = 0
x(x^3 + x^2 + x + 1) = 0
x[x^2(x + 1) + 1(x + 1)] = 0
x(x + 1)(x^2 + 1) = 0 ⇔ x = 0 or x + 1 = 0 or x^2 + 1 = 0
x = 0 or x = -1 or x^2 = -1 -false
Answer: x= 0 or x = -1.