The values of x, y and z for the system of equations x + 2y + 3z

Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

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1.

The values of x, y and z for the system of equations x + 2y + 3z = 6, 3x - 2y + z = 2 and 4x + 2y + z = 7 are respectively

  • 1, 1, 1

  • 1, 2, 3

  • 1, 3, 2

  • 2, 3, 1


A.

1, 1, 1

The given system of equations is

x + 2y + 3z = 6    ...(i)

 3x - 2y + z = 2    ...(ii)

4x + 2y + z = 7   ....(iii)

Here, A = 1233- 21421, B = 627 and x = xyz   A = 1233- 21421             = 1- 2 - 2 - 23 - 4 + 36 + 8             = - 4 + 2 + 42 = 40Now, adj A = - 4481- 118146- 8      A- 1 = 1Aadj A = 140- 4481- 118146- 8Now,      X = A- 1B = 140- 4481- 118146- 8627                 = 140- 24 + 8 + 566 - 22 + 5684 + 12 - 56 = 140404040     xyz = 111

Thus, we get x = 1, y = 1 and z = 1.


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2.

If the determinant  = 3- 2sin3θ- 78cos2θ- 11142 = 0, then the value of sinθ is

  • 13or 1

  • 12 or 32

  • 0 or 12

  • None of these


3.

The relation R in R defined by R = {(a, b): a  b3), is

  • reflexive

  • symmetric

  • transitive

  • None of these


4.

The value of 2tan-1csctan-1x - tancot-1x is

  • tan-1x

  • tan(x)

  • cot(x)

  • csc-1x


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5.

Let f (x + y) = f(x) + f(y) for all x and y. If the function f(x) is continuous at x = 0, then f(x) is continuous

  • only at x = 0

  • at x  R - 0

  • for all x

  • None of these


6.

Let fx = x2sin1x, x  00,             x = 0. Then, f(x) is continuous but not differentiable at x = 0, if

  • n  0, 1

  • n  [1, )

  • n  - , 0

  • n = 0


7.

The altitude of the right circular cone of maximum volume that can be inscribed in a sphere of radius r is

  • r2

  • r3

  • 3r4

  • 4r3


8.

If in a ABCsin3A + sin3B + sin3C = 3sinAsinBsinC, then the value of determinant abcbcacab is equal to

  • 0

  • 1

  • 2

  • 3


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9.

Let f(x) = x(x - 1)2, the point at which f(x) assumes maximum and minimum are respectively

  • 13, 1

  • 1, 13

  • 3, 1

  • None of these


10.

Rectangles are inscribed ina circle of radius r. The dimensions of the rectangle which has the maximum area, are

  • r, r

  • 2r, 2r

  • 2r, 2r

  • None of the above


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