If two distinct chords drawn from the point ( p , q ) on the circle x 2 + y 2 = p x + q y (where p q ≠…

If two distinct chords drawn from the point (p,q) on the circle x2+y2=px+qy (where pq0) are bisected by the X-axis, then
  1. p2=q2
  2. p2=8q2
  3. p2<8q2
  4. p2>8q2

Solution

Let (t, m) be the other end of the chord drawn from the point (p, q) on the circle

x2+y2=px+qy

Their mid-point is t+p2,m+q2

since, mid-point lies on X-axis i.e. y=0

m+q=0   ...(i)

Also, (t, m) lies on the circle.

 t2+m2-pt-qm=0   ...(ii)

From Eqs. (i) and (ii), we get t2-pt+2q2=0

Which is quadratic in t such that, Discriminant >0

 p2-8q2>0p2>8q2

Asked in: BITSAT 2017

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