If the tangent drawn to the hyperbola 4 y 2 = x 2 + 1 intersect the co-ordinates axes at the distinct points…

If the tangent drawn to the hyperbola 4y2=x2+1 intersect the co-ordinates axes at the distinct points A and B, then the locus of the midpoint of AB is :
  1. x2-4y2+16x2y2=0
  2. 4x2-y2+16x2y2=0
  3. x2-4y2-16x2y2=0
  4. 4x2-y2-16x2y2=0

Solution

Let tangent drawn at point x1, y1 to the hyperbola

4y2=x2+1 is 4yy1=xx1+1.

This tangent intersect coordinate axes at A and B respectively, then A-1x1, 0& B0, 14y.

Let mid point is Mh, k.

2h=-1x1x1=-12h     ...1

2k=14y1y1=18k   ...2

Since, point x1, y1, lies on the hyperbola.

So, 4y12=x12+1

From equations 1 and 2, we get

418k2=-12h2+1116k2=14h2+1

4h2=16k21+4h2

x2=4y2+16x2y2

x2-4y2-16x2y2=0 Locus of M.

Asked in: JEE Main 2018 (15 Apr)

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