1986

JEE Main 1986 Mathematics question on Straight Lines and Pair of Lines

The points (0,83)\left(0, \dfrac{8}{3}\right), (1,3)(1, 3) and (82,30)(82, 30) are vertices of
  1. A.
    an obtuse angled triangle
  2. B.
    an acute angled triangle
  3. C.
    a right angled triangle
  4. D.
    None of the above
Show answer and solution

Correct option: D

Solution

Check if the three points are collinear.

Slope from (0, 8/3) to (1, 3): (3 - 8/3)/(1 - 0) = (1/3)/1 = 1/3.

Slope from (1, 3) to (82, 30): (30 - 3)/(82 - 1) = 27/81 = 1/3.

Both slopes are equal, so all three points are collinear — they lie on the same straight line. Therefore they do not form any triangle at all, and the answer is "None of the above."

[1986]

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