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p(1),p(2),p(3) are the distances of poin...

`p_(1),p_(2),p_(3)` are the distances of points (1,1),(2,0) and (0,2) from a variable line L such that `p_(1)+p_(2)+p_(3)=0`. The line L passes through a fixed point

A

(1,2)

B

(1,1)

C

(2,1)

D

none

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To solve the problem, we need to find the equation of the variable line \( L \) that passes through a fixed point and satisfies the condition that the sum of the distances from the given points to the line is zero. ### Step-by-step Solution: 1. **Define the Variable Line**: Let the equation of the variable line \( L \) be given by: \[ Ax + By + C = 0 \] 2. **Calculate Distances**: The distances \( p_1, p_2, p_3 \) from the points \( (1, 1) \), \( (2, 0) \), and \( (0, 2) \) to the line are given by the formula for the distance from a point to a line: \[ p = \frac{|Ax_1 + By_1 + C|}{\sqrt{A^2 + B^2}} \] Thus, we can write: - For point \( (1, 1) \): \[ p_1 = \frac{|A(1) + B(1) + C|}{\sqrt{A^2 + B^2}} = \frac{|A + B + C|}{\sqrt{A^2 + B^2}} \] - For point \( (2, 0) \): \[ p_2 = \frac{|A(2) + B(0) + C|}{\sqrt{A^2 + B^2}} = \frac{|2A + C|}{\sqrt{A^2 + B^2}} \] - For point \( (0, 2) \): \[ p_3 = \frac{|A(0) + B(2) + C|}{\sqrt{A^2 + B^2}} = \frac{|2B + C|}{\sqrt{A^2 + B^2}} \] 3. **Set Up the Equation**: According to the problem, we have: \[ p_1 + p_2 + p_3 = 0 \] Substituting the distances: \[ \frac{|A + B + C|}{\sqrt{A^2 + B^2}} + \frac{|2A + C|}{\sqrt{A^2 + B^2}} + \frac{|2B + C|}{\sqrt{A^2 + B^2}} = 0 \] Since \( \sqrt{A^2 + B^2} \) is a positive quantity, we can multiply through by \( \sqrt{A^2 + B^2} \): \[ |A + B + C| + |2A + C| + |2B + C| = 0 \] 4. **Analyze the Absolute Values**: The only way for the sum of absolute values to equal zero is if each absolute value is individually zero: \[ |A + B + C| = 0, \quad |2A + C| = 0, \quad |2B + C| = 0 \] This leads to the following equations: \[ A + B + C = 0 \quad (1) \] \[ 2A + C = 0 \quad (2) \] \[ 2B + C = 0 \quad (3) \] 5. **Solve the System of Equations**: From equation (2), we can express \( C \) in terms of \( A \): \[ C = -2A \] From equation (3), we can express \( C \) in terms of \( B \): \[ C = -2B \] Setting these equal gives: \[ -2A = -2B \implies A = B \] Substituting \( C = -2A \) into equation (1): \[ A + A - 2A = 0 \implies 0 = 0 \] This confirms that \( A \) and \( B \) can take any value as long as they are equal. 6. **Final Equation of the Line**: Therefore, the equation of the line can be expressed as: \[ A(x + y) - 2A = 0 \implies x + y - 2 = 0 \] This line passes through the point \( (1, 1) \). ### Conclusion: The variable line \( L \) that satisfies the given conditions is: \[ x + y - 2 = 0 \]
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ML KHANNA-RECTANGULAR CARTESIAN CO-ORDINATE SYSTEM AND THE STRAIGHT LINE-PROBLEM SET(4)(MULTIPLE CHOICE QUESTIONS)
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