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MHT CET202613 April 2026Morning ShiftMathematicsPair of LinesActual

The joint equation of the pair of lines through the origin and making an angle of 4 with the line 3x + y - 6 = 0 is

Options

  1. A2x^2 + 3xy - 2y^2 = 0
  2. B2x^2 + 3xy + 2y^2 = 0
  3. Cx^2 + 3xy - y^2 = 0
  4. Dx^2 - 3xy + y^2 = 0

Correct answer

A. 2x^2 + 3xy - 2y^2 = 0

Step-by-step solution

Slope of the given line 3x + y - 6 = 0 is m₁ = -3 . Let m be the slope of a line passing through the origin and making an angle of 4 with the given line. Using the angle formula, ( 4 ) = | m - m₁ 1 + m m₁ | 1 = | m - (-3) 1 + m(-3) | = | m + 3 1 - 3m | Squaring both sides, we get: (1 - 3m)^2 = (m + 3)^2 1 - 6m + 9m^2 = m^2 + 6m + 9 8m^2 - 12m - 8 = 0 Dividing by 4 , we get 2m^2 - 3m - 2 = 0 . Since the lines pass through the origin, their equations are of the form y = mx , which implies m = y x . Substituting m = y

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