Answer
$y^2=-9x$
Work Step by Step
Parabola in the standard form with the vertex at origin (horizontal axis):
$y^2=4px$
$6^2=4p(-4)$
$36=-16p$
$p=-\frac{36}{16}=-\frac{9}{4}$
$y^2=4(-\frac{9}{4})x$
$y^2=-9x$
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