IIT JEE , AIEEE Forum - Mathematics , Analytical Geometry - Parabola- x^2=4y and y^2=4x...

prateek.agarwal

Parabola- x^2=4y and y^2=4x...

KAB

Eqn of tangent is y=mx+a/m and its slope is m

Differentiate 2nd eqn wrt x

So dy/dx=x/2 which is the slope of the tangent at x

Given m*x/2= -1

or x= -2/m

So 4/m^2=4y or y=1/m^2

So 1/m^2= -2+a/m

Simplifying we get 2m^2-am+1=0

For m to be real discriminant should be greater than or equal to zero.

So a^2>=8

So a>=2root2 , a<= -2root2

So the answers are a) and d)

prateek.agarwal

KAB...rated u...

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