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What is the directrix of the parabola given by the equation `x=y^2` ?

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jpwong96 | Student, Grade 10 | eNotes Newbie

Posted August 12, 2012 at 10:31 PM via web

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What is the directrix of the parabola given by the equation `x=y^2` ?

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lfryerda | High School Teacher | (Level 2) Educator

Posted August 12, 2012 at 11:24 PM (Answer #1)

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The for the parabola `y^2=4px` , the focus is found at `x=p` .  This means for the parabola `y^2=x` , the focus is at `x=1/4` .  The directrix is then the line perpendicular to the line of symmetry and equidistant from the focus and the vertex.  

That means that the directrix is the line `x=-1/4`

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