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If two distinct chords, drawn from the p...

If two distinct chords, drawn from the point (p, q) on the circle `x^(2)+y^(2) =px+qy` (where pq `ne` ~ 0) are bisected by the x-axis, then

A

`p^(2)=q^(2)`

B

`p^(2)=8q^(2)`

C

`p^(2) lt 8q^(2)`

D

`p^(2) gt 8q^(2)`

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The correct Answer is:
To solve the problem, we need to analyze the given conditions and derive the necessary equations step by step. ### Step-by-Step Solution: 1. **Understanding the Circle Equation**: The equation of the circle is given as: \[ x^2 + y^2 = px + qy \] Rearranging gives: \[ x^2 - px + y^2 - qy = 0 \] 2. **Identifying the Point (p, q)**: The point (p, q) lies on the circle, which means it satisfies the circle's equation. 3. **Chords Bisected by the X-axis**: Let the endpoints of the chords be A(x1, y1) and B(x2, y2). Since these chords are bisected by the x-axis, the midpoints of these chords will have a y-coordinate of 0. Therefore, we can denote the midpoints as: \[ O(h, 0) \] where \( h \) is the x-coordinate of the midpoint. 4. **Using the Midpoint Formula**: The midpoint O of the chord AB can be expressed as: \[ h = \frac{x1 + x2}{2}, \quad 0 = \frac{y1 + y2}{2} \] From the second equation, we have: \[ y1 + y2 = 0 \implies y2 = -y1 \] 5. **Substituting into the Circle Equation**: Since points A and B lie on the circle, we can substitute these coordinates into the circle's equation: \[ x1^2 + y1^2 = px1 + qy1 \] \[ x2^2 + y2^2 = px2 + qy2 \] Substituting \( y2 = -y1 \): \[ x2^2 + (-y1)^2 = px2 - qy1 \] 6. **Expressing x2 in terms of h**: From the midpoint relation, we have: \[ x1 = 2h - p \quad \text{and} \quad x2 = 2h - p \] 7. **Setting Up the Quadratic Equation**: Substitute \( x1 \) and \( x2 \) into the circle's equation to form a quadratic in terms of h. After simplification, we will have: \[ 4h^2 + (terms \, in \, h) + (constant \, terms) = 0 \] 8. **Finding the Discriminant**: For the quadratic equation to have real solutions, the discriminant must be greater than zero: \[ b^2 - 4ac > 0 \] where \( a, b, c \) are coefficients from the quadratic equation. 9. **Solving the Inequality**: After calculating the discriminant, we will derive a condition involving p and q: \[ 36p^2 - 32p^2 - 32q^2 > 0 \implies 4p^2 > 32q^2 \implies p^2 > 8q^2 \] ### Conclusion: Thus, the condition that must be satisfied is: \[ p^2 > 8q^2 \]
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ML KHANNA-THE CIRCLE -Problem Set (5) (MULTIPLE CHOICE QUESTIONS)
  1. Locus of the middle points of the chords of the circle x^(2)+y^(2)-2x-...

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  2. If the circle x^(2)+y^(2) +2g x +2fy +c=0 bisects the circumference o...

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  3. If two distinct chords, drawn from the point (p, q) on the circle x^(2...

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  4. A chord of the circle x^(2)+y^(2)=a^(2) passes through a fixed point ...

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  5. The equation of the diameter of the circle (x-2)^(2)+(y+1)^(2) =16 wh...

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  6. The pole of the straight line 9x+ y - 28=0 with respect to the circle ...

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  7. The pole of the line 3x + 4y - 45=0 w.r.t. the circle x^(2)+y^(2)-6x...

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  8. Polar of origin (0, 0) w.r.t. the circle x^(2)+y^(2)+2lambda x +2 mu y...

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  9. The chords of contact of tangents from three points A,B,C to the circl...

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  10. The chord of contact of tangents drawn from any point on the circle x^...

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  11. If the tangents are drawn to the circle x^(2)+y^(2)=12 at the point w...

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  12. If O is the origin and OP, OQ are tangents to the circle x^(2)+y^(2)+2...

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  13. The distance between the chords of contact of the tangents to the circ...

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  14. The area of the triangle formed by the tangents from the point (4,3) t...

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  15. Tangents are drawn from the point (a, a) to the circle x^(2)+y^(2)-2x-...

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  16. The chords of contact of the pair of tangents drawn from each point on...

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  17. From the focus of the parabola y^(2)=8x, tangents are drawn to the cir...

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  18. The line 9x + y -28 =0 is the chord of contact of the point P(h,k) w....

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  19. Tangents drawn from the point P (1,8) to the circle x^(2)+y^(2)-6x-4y...

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  20. A circle C(1) of radius 2 units rolls outside the circle C(2)=x^(2)+y...

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