## anonymous one year ago Find the standard form of the equation of the parabola with a focus at (0, -10) and a directrix at y = 10. How would I solve this?

1. ganeshie8

Notice that the vertex is $$(0,0)$$ here because it is the midpoint between focus and directrix line. Since the focus is below the directrix line, the parabola faces downwards : $y = -\frac{1}{4a}x^2$

2. anonymous

y=-(1/40)x^2?

3. ganeshie8

where $$a$$ is the distance between "focus" and "vertex" |dw:1437708887336:dw|

4. anonymous

20?

5. ganeshie8

|dw:1437709113428:dw|

6. ganeshie8

y=-(1/40)x^2? is correct

7. anonymous

Thank you very much!

8. ganeshie8

yw