18 ➗ (-4 1/2) with explanation
1 answer:
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For this case we have a function of the formwhere:
We must find the value of the function when. So:
By definition we have to:
Thus, the value of the function is
Answer:
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>
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,
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>