Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

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11.

The minimum value of the function f(x) = 2x3 - 21x2 + 36x - 20 is

  • - 128

  • - 126

  • - 120

  • None of these


D.

None of these

Given, fx = 2x3 - 21x2 + 36x - 20      f'x = 6x2 - 42x + 36and   f''x = 12x - 42For maxima or minima, put f' (x) = 0  6x2 - 42x + 36 = 0   x2 - 7x + 6 = 0 x - 6x - 1 = 0                     x = 1, 6At x = 1, f''1 = 12 - 42 = - 30 < 0 f(x) is maximum x = 1Hence, maximum value offx = 2 - 21 + 36 - 20     = 38 - 41 = - 3


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12.

If the function f(x) = 2x3 - 9ax2 + 12a + 1, where a > 0, attains its maximum and minimum values at p and q respectively such that p2 = q, then a equals

  • 3

  • 1

  • 2

  • 12


13.

If 2a + 3b + 6c = 0, then at least one root of the equation ax2 + bx + c = 0 lies in the inverval

  • (0, 1)

  • (1, 2)

  • (2, 3)

  • (1, 3)


14.

If aa21 + a3bb21 + b3cc21 + c3 and vectors (1, a, a2), (1, b, b2) and (1, c, c2) are non-coplanar, then the product abc equals

  • 2

  • - 1

  • 1

  • 0


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15.

If the length of perpendicular drawn from origin on a plane is 7 unit and its direction ratios are - 3, 2 and 6, then that plane is

  • - 3x + 2y + 6z - 7 = 0

  • - 3x + 2y + 6z - 49 = 0

  • 3x - 2y + 6z + 7 = 0

  • - 3x + 2y - 6z - 49 = 0


16.

The shortest distance from the plane 12x + 4y + 3z = 327 to the sphere x2 + y2 + z2 + 4x - 2y - 6z = 155,is

  • 26

  • 11413

  • 13

  • 39


17.

The acute angle between the line joining the points (2, 1, - 3), (- 3, 1, 7)and a line parallel to x - 13 = y4 = z + 35, through the point (- 1, 0, 4), is

  • cos-17510

  • cos-1110

  • cos-13510

  • cos-11510


18.

Two systems ofrectangular axis have the same origin. If a plane cuts them at distances a, b, c and d', b', c' from the origin, then

  • 1a2 + 1b2 + 1c2 + 1a'2 + 1b'2 + 1c'2 = 0

  • 1a2 + 1b2 - 1c2 + 1a'2 + 1b'2 - 1c'2 = 0

  • 1a2 - 1b2 - 1c2 + 1a'2 - 1b'2 - 1c'2 = 0

  • 1a2 + 1b2 + 1c2 - 1a'2 - 1b'2 - 1c'2 = 0


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19.

If a plane passes through the point (1, 1, 1) and is perpendicular to the line x - 13 = y - 10 = z - 14 then its perpendicular distance from the origin is

  • 34

  • 43

  • 75

  • 1


20.

The intersection of the spheres x2 + y2 + z2 + 7x - 2y - z = 13 and x2 + y2 + z2 - 3x + 3y + 4z = 8 is the same as the intersection of one of the sphere and the plane

  • x - y - z = 1

  • x - 2y - z = 1

  • x - y - 2z = 1

  • 2x - y - z = 1


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