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# If the focus of a parabola is $(0,-3)$ and its directrix is $y=3$,then its equation is

$\begin{array}{1 1}x^2=-12y\\x^2=12y\\y^2=-12x\\y^2=12x\end{array}$

• Equation of a parabola which is open downwards is given by $x^2=-4ay$ where $a$ is the focus of the parabola.
Answer : $x^2=-12y$
Given the focus of the parabola is $(0,-3)$ and directrix is $y=3$
Hence its equation is of the form $x^2=-4ay$
Since $a=3$
The required equation is $x^2=-4\times 3y=-12y$