Answer:

Step-by-step explanation:
We want to find the equation of a parabola with vertex (0,5), focus at (0,7) and directrix y=3.
This is given by 
where p=2, h=0, and k=5
We substitute these values to get:

This simplifies to:

We solve for y to get:

Answer:
Step-by-step explanation:
Let 
Subbing in:

a = 9, b = -2, c = -7
The product of a and c is the aboslute value of -63, so a*c = 63. We need 2 factors of 63 that will add to give us -2. The factors of 63 are {1, 63}, (3, 21}, {7, 9}. It looks like the combination of -9 and +7 will work because -9 + 7 = -2. Plug in accordingly:

Group together in groups of 2:

Now factor out what's common within each set of parenthesis:

We know this combination "works" because the terms inside the parenthesis are identical. We can now factor those out and what's left goes together in another set of parenthesis:

Remember that 
so we sub back in and continue to factor. This was originally a fourth degree polynomial; that means we have 4 solutions.

The first two solutions are found withing the first set of parenthesis and the second two are found in other set of parenthesis. Factoring
gives us that x = 1 and -1. The other set is a bit more tricky. If
then
and

You cannot take the square root of a negative number without allowing for the imaginary component, i, so we do that:
±
which will simplify down to
±
Those are the 4 solutions to the quartic equation.
Circumference = pi*diameter
C = pi*20
C = 20pi
When I used my calculator to compute 20*pi, I get approximately 62.83185
This is somewhat close to what choice C is saying. The difference is that choice C has an extra 1 buried inside it. I'm not sure if your teacher made a typo.
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