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JEE Main20208 Jan 2020Morning ShiftMathematicsStraight LinesActual

Let two points be A 1 , - 1 and B 0 , 2 . If a point P x ' , y ' be such that the area of ∆ P A B = 5 sq. units and it lies on the line 3 x + y - 4 λ = 0 , then a value of λ is

Options

  1. A4
  2. B3
  3. C1
  4. D- 3

Correct answer

B. 3

Step-by-step solution

∆ = 1 2 0 2 1 1 - 1 1 x ' y ' 1   ⇒ - 2 1 - x ' + y ' + x ' = ± 10 ⇒ - 2 + 2 x ' + y ' + x ' = ± 10 ⇒ 3 x ' + y ' = 12 Or 3 x ' + y ' = - 8   . . . i x ' ,   y ' lies on the line 3 x + y - 4 λ = 0 , So, 3 x ' + y ' - 4 λ = 0 . . . i i Solving i and i i , we get,           λ = 3 ,   - 2

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