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Three Dimensional Geometry · Question 49

JEE Main 2025 (Online) 2nd April Evening ShiftMCQEasy📈 Topic in 35% papers+4−1
1

The line L1 is parallel to the vector a = -3 i + 2 j + 4 k and passes through the point (7, 6, 2) and the line L2 is parallel to the vector b = 2 i + j + 3 k and passes through the point (5, 3, 4). The shortest distance between the lines L1 and L2 is :

  1. 23 38
  2. 21 38
  3. 23 57
  4. 21 57

Answer

(1) 23 38

Solution

a b = vmatrix i & j & k \ -3 & 2 & 4 \ 2 & 1 & 3 vmatrix

= (6 - 4) i - (-9 - 8) j + (-3 - 4) k = 2 i + 17 j - 7 k

| a b| = 4 + 289 + 49 = 342 = 3 38

Vector joining the given points: (5 - 7) i + (3 - 6) j + (4 - 2) k = -2 i - 3 j + 2 k

SD = |(-2 i - 3 j + 2 k) (2 i + 17 j - 7 k)|| a b|

= |-4 - 51 - 14|3 38 = 693 38 = 23 38

Answer: (1)

JEE Main 2025 (Online) 2nd April Evening Shift

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2

Let L1 : x-11 = y-2-1 = z-12 and L2 : x+1-1 = y-22 = z1 be two lines. Let L3 be a line passing through the point ( , , ) and be perpendicular to both L1 and L2. If L3 intersects L1, then |5 - 11 - 8 | equals :

  1. 25
  2. 20
  3. 16
  4. 18
JEE Main 2025 (Online) 29th January Morning Shift
3

Let a = i + 2 j + k and b = 2 i + 7 j + 3 k. Let L1 : r = (- i + 2 j + k) + a, R and L2 : r = ( j + k) + b, R be two lines. If the line L3 passes through the point of intersection of L1 and L2 and is parallel to a + b, then L3 passes through the point :

  1. (-1, -1, 1)
  2. (2, 8, 5)
  3. (8, 26, 12)
  4. (5, 17, 4)
JEE Main 2025 (Online) 29th January Morning Shift
4

If the image of the point (4, 4, 3) in the line x - 12 = y - 21 = z - 13 is ( , , ), then + + is equal to

  1. 12
  2. 9
  3. 7
  4. 8
JEE Main 2025 (Online) 28th January Morning Shift
5

The square of the distance of the point ( 157, 327, 7 ) from the line x+13 = y+35 = z+57 in the direction of the vector i + 4 j + 7 k is:

  1. 66
  2. 54
  3. 41
  4. 44
JEE Main 2025 (Online) 28th January Evening Shift

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