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📐 Mathematics  ·  Straight Lines  ·  JEE

The image of the point (3, 8) in the line x + 3y = 7 is:

Answer: (−1, −4).

  • A (−1, −4)
  • B (1, 4)
  • C (−1, 4)
  • D (1, −4)

Correct answer: A. (−1, −4)

Explanation: With a=1, b=3, value = 3+24−7 = 20 and a²+b² = 10. Image = (3 − 2·1·20/10, 8 − 2·3·20/10) = (−1, −4).

Slope as Rise over Runxy(x₁,y₁)(x₂,y₂)run = x₂−x₁rise = y₂−y₁m = rise/run = (y₂−y₁)/(x₂−x₁) = tanθ

The slope of a line is the ratio of vertical change (rise) to horizontal change (run) between any two points on it - equivalently, the tangent of the angle θ the line makes with the positive x-axis.

Concept context

Points, lines, and curves on the Cartesian plane

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