If the pair of lines ax2 + 2 (a + b)xy + by 2 = 0 lie along diameters ...
As per question area of one sector = 3 area of another sector
⇒ angle at centre by one sector = 3x angle at centre by another sector
Let one angle be θ then other = 3θ
Clearly θ + 3θ = 180 ⇒ θ = 45o
∴ Angle between the diameters represented by combined equation
ax2 + 2 ( a + b ) xy + by2 = 0 is 45o
∴ Using

we get

⇒ a2 + b2 + 2ab = 4a2 + 4b2 +4ab ⇒ 3a2 + 3b2 + 2ab = 0
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If the pair of lines ax2 + 2 (a + b)xy + by 2 = 0 lie along diameters ...
Understanding the Problem
The problem involves a pair of lines represented by the equation ax^2 + 2(a + b)xy + by^2 = 0. These lines are diameters of a circle, dividing it into four sectors. The key condition is that the area of one sector is three times that of another.
Conditions for Diameters
- For the lines to be diameters, their slopes must be negative reciprocals.
- The angle between the two lines must be 90 degrees, ensuring they meet at the center of the circle.
Area Relationship
- Let the areas of the sectors be A and 3A.
- The total area of the circle is divided into four sectors, so we have A + 3A = Area of Circle = πr².
- From this, we derive that the total area (4A) implies that A must be πr²/4.
Finding the Condition
To find the condition on a and b, we analyze the quadratic equation and apply the relationship derived from the slopes of the diameters.
- The discriminant of the quadratic must be non-negative.
- We need to establish the relationship based on the given area ratio.
Conclusion: The Correct Condition
Upon solving the equations and substituting the conditions, we arrive at:
- 3a² + 2ab + 3b² = 0
Thus, the correct answer is option 'D'.
This relationship ensures that the areas of the sectors maintain the specified ratio, satisfying the problem's requirements.