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NDA 2018 Maths · Mathematics · Straight Lines · easy

The equation of the directrix of the parabola y^2=-6x is

Single correct option

The equation of the directrix of the parabola y2=−6xy^2=-6x is
  1. A. 2x+3=02x+3=0
  2. B. x=3x=3
  3. C. y=32y=\frac32
  4. D. 2x=32x=3
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Answer: (D) 2x=32x=3

Here 4a=64a=6, so a=32a=\frac32. The parabola opens to the left, with the focus at (−32,0)\left(-\frac32,0\right) and the directrix on the opposite side, x=32x=\frac32, i.e. 2x=32x=3. The option 2x+3=02x+3=0 is the directrix of y2=6xy^2=6x.
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Original question written in the NDA 2018 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake