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Three Dimensional Geometry · Question 17

JEE Main 2026 (Online) 2nd April Evening ShiftMCQMedium📈 Topic in 68% papers+4−1
1

Let the point A be the foot of perpendicular drawn from the point P(a, b, 0) on the line x-12= y-21= z- 3. If the midpoint of the line segment PA is (0, 34, - 14 ), then the value of a2+b2+ 2 is equal to :

  1. 1
  2. 2
  3. 6
  4. 9

Answer

(1) 1

Solution

Midpoint of PA is (0, 34, - 14 ) and P(a, b, 0)

A= (-a, 32-b, - 12 )

PA= (-2a, 32-2b, - 12 ) (2, 1, 3)

-4a+ 32-2b- 32=0 b=-2a

A on the line: -a=1+2t, 32-b=2+t, - 12= +3t

a=-1-2t, b=- 12-t

b=-2a - 12-t=2+4t t=- 12

a=0, b=0, =- 12+ 32=1

(Check: A (0, 32, - 12 ) gives - 12 in each ratio of the line)

a2+b2+ 2=0+0+1=1

Answer: (1)

JEE Main 2026 (Online) 2nd April Evening Shift

Keep practising — Three Dimensional Geometry

2

If the distances of the point (1, 2, a) from the line x - 11 = y2 = z - 11 along the lines L1 : x - 13 = y - 24 = z - ab and L2 : x - 11 = y - 24 = z - ac are equal, then a + b + c is equal to

  1. 4
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  4. 5
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3

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  1. 8
  2. 7
  3. 6
  4. 5
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4

If the distance of the point P(43, , ), < 0, from the line r = 4 i - k + (2 i + 3 k), R along a line with direction ratios 3, -1, 0 is 13 10, then 2 + 2 is equal to

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5

Let the lines L1: r = i + 2 j + 3 k + (2 i + 3 j + 4 k), R and L2: r = (4 i + j) + (5 i + 2 j + k), R, intersect at the point R. Let P and Q be the points lying on lines L1 and L2, respectively, such that | PR| = 29 and | PQ| = 473. If the point P lies in the first octant, then 27(QR)2 is equal to

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6

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7

The sum of all values of , for which the shortest distance between the lines x+1 = y-2-1 = z-4- and x = y-12 = z-12 is 2, is

  1. -6
  2. -8
  3. 8
  4. 6
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8

Let the direction cosines of two lines satisfy the equations : 4l + m - n = 0 and 2mn + 10nl + 3lm = 0. Then the cosine of the acute angle between these lines is :

  1. 107 38
  2. 10 38
  3. 103 38
  4. 203 38
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9

The vertices B and C of a triangle ABC lie on the line x1 = 1 - y-2 = z - 23. The coordinates of A and B are (1, 6, 3) and (4, 9, α) respectively and C is at a distance of 10 units from B. The area (in sq. units) of ABC is :

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  2. 5 13
  3. 15 13
  4. 10 13
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10

If the image of the point P(a, 2, a) in the line x2 = y + a1 = z1 is Q and the image of Q in the line x - 2b2 = y - a1 = z + 2b-5 is P , then a + b is equal to .

JEE Main 2026 (Online) 23rd January Evening Shift
11

Let P( , , ) be the point on the line x - 12 = y + 1-3 = z at a distance 4 14 from the point (1, -1, 0) and nearer to the origin. Then the shortest distance, between the lines x - 1 = y - 2 = z - 3 and x + 52 = y - 101 = z - 31, is equal to

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  2. 7 54
  3. 4 57
  4. 2 74
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