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Find the equation of the straight line through the point (α, β) and perpendicular to the line lx + my + n = 0.

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Question

Find the equation of the straight line through the point (α, β) and perpendicular to the line lx + my + n = 0.

Answer in Brief
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Solution

The line perpendicular to lx + my + n = 0 is \[mx - ly + \lambda = 0\]

This line passes through (α, β). 

\[\therefore m\alpha - l\beta + \lambda = 0\]

\[ \Rightarrow \lambda = l\beta - m\alpha\]

Substituting the value of \[\lambda\]: 

\[mx - ly + l\beta - m\alpha = 0\]

\[ \Rightarrow m\left( x - \alpha \right) = l\left( y - \beta \right)\]

This is equation of the required line.

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Equations of Line in Different Forms - Equation of Family of Lines Passing Through the Point of Intersection of Two Lines
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Chapter 23: The straight lines - Exercise 23.12 [Page 92]

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R.D. Sharma Mathematics [English] Class 11
Chapter 23 The straight lines
Exercise 23.12 | Q 7 | Page 92

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