JEE Main 2015 · 11 Apr · Shift 1 · Mathematics Q82

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MathematicsSingle correct+4 / -1Question 82 of 90

Let PQ be a double ordinate of the parabola, $y^2=-4x$ , where P lies in the second quadrant. If R divides PQ in the ratio 2 : 1, then the locus of R is :

9y^2=4x

9y^2=-4x

3y^2=2x

3y^2=-2x

Answer and worked solution

Official answer: B

$P(-t^2,2t)$ with $t>0$ and $Q(-t^2,-2t)$ . R divides PQ in the ratio 2 : 1: $R=\left(-t^2,-\frac{2t}3\right)$ . Eliminating $t$ : $9y^2=-4x$ .

Topics:Parabola Locus

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JEE Main 2015 · 11 Apr · Shift 1, Mathematics question 82