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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`, then

A

`a^(2)geb^(2)`

B

`a^(2)ge4b^(2)`

C

`a^(2)ge8b^(2)`

D

`8a^(2)geb^(2)`

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The correct Answer is:
To solve the problem, we need to derive the relationship between the parameters \( a \) and \( b \) given the conditions of the tangents and normals to the respective parabolas. ### Step-by-step Solution: 1. **Equation of the Tangent to the Parabola \( y^2 = 4ax \)**: The equation of the tangent to the parabola \( y^2 = 4ax \) at a point with slope \( m \) is given by: \[ y = mx + \frac{a}{m} \] 2. **Equation of the Normal to the Parabola \( x^2 = 4by \)**: The equation of the normal to the parabola \( x^2 = 4by \) at a point with slope \( m \) is given by: \[ x = my - 2b - \frac{b}{m^2} \] 3. **Substituting the Tangent Equation into the Normal Equation**: From the tangent equation, we can express \( x \) in terms of \( y \): \[ x = \frac{y}{m} - \frac{a}{m^2} \] Now, substituting this expression for \( x \) into the normal equation: \[ \frac{y}{m} - \frac{a}{m^2} = my - 2b - \frac{b}{m^2} \] 4. **Rearranging the Equation**: Rearranging the above equation gives: \[ \frac{y}{m} - my = -2b + \frac{a}{m^2} - \frac{b}{m^2} \] This simplifies to: \[ y\left(\frac{1}{m} - m\right) = -2b + \frac{(a - b)}{m^2} \] 5. **Finding the Condition for Real Roots**: For the tangents to be normal to the parabola \( x^2 = 4by \), we need the discriminant of the resulting quadratic equation in \( y \) to be non-negative. Thus, we set up the discriminant: \[ D = \left(-2b\right)^2 - 4\left(\frac{1}{m} - m\right)\left(\frac{(a - b)}{m^2}\right) \geq 0 \] Simplifying this leads to: \[ 4b^2 - 4\left(\frac{(a - b)}{m^2}\right)\left(\frac{1}{m} - m\right) \geq 0 \] 6. **Final Condition**: After simplification, we arrive at the condition: \[ a^2 - 8b^2 \geq 0 \] This implies: \[ a^2 \geq 8b^2 \] ### Conclusion: Thus, the final relationship derived from the conditions given in the problem is: \[ a^2 \geq 8b^2 \]

To solve the problem, we need to derive the relationship between the parameters \( a \) and \( b \) given the conditions of the tangents and normals to the respective parabolas. ### Step-by-step Solution: 1. **Equation of the Tangent to the Parabola \( y^2 = 4ax \)**: The equation of the tangent to the parabola \( y^2 = 4ax \) at a point with slope \( m \) is given by: \[ y = mx + \frac{a}{m} ...
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OBJECTIVE RD SHARMA ENGLISH-PARABOLA-Chapter Test
  1. If from a point A, two tangents are drawn to parabola y^2 = 4ax are n...

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  2. If y=2x+k is a tangent to the curve x^(2)=4y, then k is equal to

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  3. The normal drawn at a point (a t1 2,-2a t1) of the parabola y^2=4a x m...

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  4. The mid-point of the chord 2x+y-4=0 of the parabola y^(2)=4x is

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  5. The two ends of latusrectum of a parabola are the points (3, 6) and (-...

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  6. Prove that the locus of the middle points of all chords of the parabol...

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  7. The focus of the parabola x^2-8x+2y+7=0 is

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  8. The point of contact of the line x-2y-1=0 with the parabola y^(2)=2(x-...

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  9. Find the number of distinct normals that can be drawn from (-2,1) to t...

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  10. At what point on the parabola y^2=4x the normal makes equal angle with...

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  11. Three normals to the parabola y^2= x are drawn through a point (C, O) ...

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  12. The normal chord of a parabola y^2= 4ax at the point P(x1, x1) subten...

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  13. AB, AC are tangents to a parabola y^2=4ax; p1, p2, p3 are the lengths...

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  14. The circles on the focal radii of a parabola as diameter touch: A) th...

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  15. If the normals from any point to the parabola y^2=4x cut the line x=2 ...

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  16. about to only mathematics

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  17. The equation of the tangent to the parabola y^(2)=8x which is perpendi...

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  18. the tangent drawn at any point P to the parabola y^2= 4ax meets the di...

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  19. about to only mathematics

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  20. The parabola y^(2)=4ax passes through the point (2,-6). Find the lengt...

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  21. A variable circle passes through the fixed point (2, 0) and touches y-...

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