The solution of the differential equation (3.xy + y2)dx + (x2 + x

Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

21.

A parents has two children. If one of them is boy, then the probability that other is, also a boy, is

  • 1/2

  • 1/4

  • 1/3

  • None of these


22.

For the LPP Min z = x1 + x2 such that inequalities 5x1 + 10x2 0, x1 + x2  1, x2  4 and x1, x2 > 0

  • There is a bounded solution

  • There is no solution

  • There are infinite solutions

  • None of these


23.

The equation of the plane containing the line x + 1- 3 = y - 32 = z + 21 and the point (0, 7, - 7) is

  • x + y + z = 1

  • x + y + z = 2

  • x + y + z = 0

  • None of these


24.

Angle of intersection of the curve r = sinθ + cosθ and r = 2sinθ is equal to

  • π2

  • π3

  • π4

  • None of these


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25.

The volume of solid generated by revolving about the y-axis the figure bounded by the parabola y = x and x = y2 is

  • 215π

  • 245π

  • 215π

  • 524π


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26.

The solution of the differential equation (3.xy + y2)dx + (x2 + xy)dy = 0 is

  • x2(2xy + y2) = c2

  • x2(2xy - y2) = c2

  • x2(y2 - 2xy) = c2

  • None of these


A.

x2(2xy + y2) = c2

Homogeneous equation can be written in the form of

dydx = - 3xy +y2x2 + xyPut y = vx and dydx = v + xdvdx, we getv + xdvdx = - 3x2v + x2v2x2 + x2v  xdvdx = - 2vv + 2v + 1  1xdx = - v + 12vv + 2dvOn integrating, we get     - 2logex = 12logv + 2 + 12logv - logc vv + 2x4 = c2 yxyx + 2 = c2          v = yx

Hence, required solution is (y2 + 2xy)x2 = c2


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27.

The order and degree of the differential equation dydx - 4dydx - 7x = 0 are

  • 1 and 1/2

  • 2 ana 1

  • 1 and 1

  • 1 and 2


28.

If the vectors i^ - 3j^ + 2k^- i^ + 2j^ represents the diagonals of a parallelogram, then its area will be

  • 21

  • 212

  • 221

  • 214


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29.

The position vector of the points A, B, C are 2i^ + j^ - k^3i^ - 2j^ + k^ and i^ + 4j^ - 3k^ respectively. These points

  • form an isosceles triangle

  • form a right angled triangle

  • are collinear

  • form a scalene triangle


30.

A random variable X has the probability distribution
x 1 2 3 4 5 6 7 8
P(x) 0.15 0.23 0.12 .010 0.20 0.08 0.07 0.05

For the events E = {x is prime number} and F = {x < 4} the probability of P(E ∪ F) is

  • 0.50

  • 0.77

  • 0.35

  • 0.87


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