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If from a point A, two tangents are drawn to parabola `y^2 = 4ax` are normal to parabola `x^2 = 4by`, thenA. `a^(2)geb^(2)`B. `a^(2)ge4b^(2)`C. `a^(2)ge8b^(2)`D. `8a^(2)geb^(2)` |
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Answer» Correct Answer - C The equation of a tangent to `y^(2)=4ax` is `y=mx+a/mrArrx=y/m-a/m^(2)" ...(i)"` This will be a normal to the parabola `x^(2)=4by`, if it is of the form `x=y/m-(2b)/m-b/m^(3)" ...(ii)"` `:." "-a/m^(2)=-(ab)/m-b/m^(3)rArr2bm-am+b=0` Since m is real. `:." "a^(2)-8b^(2)ge0rArra^(2)ge8b^(2)` |
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