Suppose the radius of circle a is equal to the diameter of circle
1 answer:
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We have the equation
Let's complete the square, to do it let's add and subtract 25 on the right side
Now we can have y in function of x
Now we can already identify the vertex because it's in the vertex form:
Where the vertex is
As we can see, h = 5 and k = -2, then the vertex is
Now we can continue and find the focus, the focus is
We have a = 1/20, therefore
The focus is
And the last one, the directrix, it's
Then
Hence the correct answer is: vertex (5, -2); focus (5, 3); directrix y = -7