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📐 Mathematics  ·  Straight Lines  ·  JEE

The value of k for which 3x + ky = 1 passes through the intersection of x + 2y = 3 and 2x + y = 3 is:

Answer: −2.

  • A 2
  • B −2
  • C 1
  • D −1

Correct answer: B. −2

Explanation: The lines meet at (1, 1). Then 3 + k = 1, so k = −2.

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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