Answer:
y = -1/10x^2 -1/2
Step-by-step explanation:
The equation for a parabola with focus (a, b) and directrix y = d is ...
y = 1/(2(b -d))(x -a)² +(b +d)/2
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For the given focus and directrix, we have ...
Simplified, the equation is ...
y = -1/10x² -1/2