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The equation of the directrix of the parabola with vertex at the originand having the axis along the x-axis and a common tangent of slope 2 with thecircle `x^2+y^2=5`is (are)`x=10`(b) `x=20``x=-10`(d) `x=-20`A. x=10B. x=20C. x=-10D. x=-20 |
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Answer» Correct Answer - A::C 1,3 The line y=2x+c ix a tangent to `x^(2)+y^(2)=5`. If `c^(2)=25`, then `c=pm5`. Let the equation of the parabola be `y^(2)=4ax`. Then `(a)/(2)=pm5` `ora=pm10` So, the equation of the parabola is `y^(2)=pm40x`. Also, the equation of the directrices are `x=pm10`. |
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