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NCERT Solutions for class 12 Maths | Chapter 9 - Differential Equations

(1)
[A]
[B]
[C]
[D]
Answer:
(2) The solution of the differential equation cos x sin y dx + sin x cos y dy = 0 is
[A] sinx/siny=c
[B] sin x sin y = c
[C] sin x + sin y = c
[D] cos x cos y = c
Answer: sin x sin y = c

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(3) The solution of the differential equation is
[A] y = tan-1 x
[B] y – x = k(1 + xy)
[C] x = tan-1 y
[D] tan(xy) = k
Answer: y – x = k(1 + xy)
(4) The differential equation satisfied by y = A/x + B is (A, B are parameters)
[A] x2 y1 = y
[B] xy1 + 2y2 = 0
[C] xy2 + 2y1 = 0
[D] none of these
Answer: xy2 + 2y1 = 0
(5) The differential equation whose solution is (x – h)2 + (y – k)2 = a2 is (a is a constant)
[A]
[B]
[C]
[D] None of these
Answer:
(6) The degree of the differential equation
[A] 2
[B] 1
[C] 3
[D] none of these
Answer: 2
(7) The degree of the equation satisfying the relation

[A] 1
[B] 2
[C] 3
[D] None of these
Answer: 1
(8) The differential equation of all parabolas whose axis of symmetry is along the axis of the x-axis is of order
[A] 3
[B] 1
[C] 2
[D] none of these
Answer: 2
(9) Given the differential equation

Mark out the correct statement.

[A] solution is y2 – sin y = -2x3 + C
[B] solution is y2 + sin y = 2x3 + C
[C] C = π2+ 2√2
[D] C = π2 + 2
Answer: solution is y2 + sin y = 2x3 + C
(10) The equation of family of curves for which the length of the normal is equal to the radius vector is
[A] y2∓x2=k2
[B] y±x=k
[C] y2 = kx
[D] none of these
Answer: y2∓x2=k2
(11) The differential equation of all parabolas whose axes are along x-axis is
[A]
[B]
[C]
[D]
Answer:
(12) The differential equation representing the family of ellipses with centre at origin and foci on x-axis is given as
[A] xy’ + y = 0
[B] x2y2(y”)2 + yy’= 0
[C] xyy” + x(y’)2 – yy’ = 0
[D] None of these
Answer: x2y2(y”)2 + yy’= 0
(13) The differential equation of the family of circles touching the x-axis at origin is given by
[A]
[B]
[C]
[D] None of these
Answer:
(14) The differential equation of all circles which pass through the origin and whose centre lies on y-axis is
[A]
[B]
[C]
[D]
Answer:
(15)
[A]
[B]
[C]
[D]
Answer:
(16)
[A] π/3
[B] π/4
[C] π/6
[D] π/12
Answer: π/12
(17)
[A]
[B]
[C]
[D]
Answer:
(18) The differential equation of all parabolas whose axes are parallel to y-axis is
[A]
[B]
[C]
[D]
Answer:
(19) The solution of differential equation (ey + 1) cosx dx + ey sinx dy = 0 is
[A] (ey + 1) sinx = c
[B] ex sinx = c
[C] (ex + 1) cosx = c
[D] none of these
Answer: (ey + 1) sinx = c
(20) If sinx dy/dx + y cosx = x sinx, then (y – 1) sinx =
[A] c – x sinx
[B] c + xcosx
[C] c – x cos x
[D] c + x sin x
Answer: c – x cos x

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