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Question
Find the equation of the straight line passing through (1, 2) and perpendicular to the line x + y + 7 = 0.
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Solution
Let m be the slope of the line whose equation is to be found out which is perpendicular to the line x + y + 7 = 0.
The slope of the given line y = (– 1)x – 7 is – 1.
Therefore, using the condition of perpendicularity of lines
We have m × (– 1) = – 1 or m = 1 (Why?)
Hence, the required equation of the line is y – 1
= (1)(x – 2) or y – 1
= x – 2x – y – 1
= 0.
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