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📐 Mathematics  ·  Straight Lines  ·  JEE

The centre of circle x² + y² - 6x + 8y + 5 = 0 is:

Answer: (3,-4).

  • A (3,-4)
  • B -3,4)
  • C (-3,-4)
  • D (6,-8)

Correct answer: A. (3,-4)

Explanation: General form: x² + y² + 2gx + 2fy + c = 0. Centre = (-g,-f). 2g = -6, g = -3; 2f = 8, f = 4. Centre = (3,-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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