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The length of the latus rectum of the parabola whose vertex is $(2 ,-3)$ and the directrix $x=4$ is

$\begin {array}{1 1}(1)2&(2)4\\(3)6&(4)8\end{array}$

Can you answer this question?

Vertex is (2,-3)
Equation of the directrix $x=4$
a= distance of the directrix from the vertex
a= x- distance of the directrix from the vertex.
$a=4-2=2$
=> $4a=8$
Hence 4 is the correct answer.
answered May 15, 2014 by