Qus : 2
AMU MCA PYQ
3
The general solution of the differential equation
$(D^2 - a^2)^3 y = e^{ax}$, where $D=\frac{d}{dx}$ is
1
$(c_1+c_2x)e^{ax}+(c_3+c_4x)e^{-ax}+\frac{x^2e^{ax}}{8a^2}$ 2
$(c_1+c_2x+c_3x^2)e^{ax}+(c_4+c_5x+c_6x^2)e^{-ax}
+\frac{x^2e^{ax}}{8a^3}$ 3
$(c_1+c_2x+c_3x^2)e^{ax}+(c_4+c_5x+c_6x^2)e^{-ax}
+\frac{x^2e^{ax}}{8a^2}$ 4
$(c_1+c_2x+c_3x^2)e^{ax}+(c_4+c_5x+c_6x^2)e^{-ax}
+\frac{xe^{ax}}{8a}$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2020 PYQ
Solution Characteristic equation:
$(m^2-a^2)^3=0$
Roots: $m=\pm a$ each of multiplicity 3.
Hence complementary function:
$(c_1+c_2x+c_3x^2)e^{ax}+(c_4+c_5x+c_6x^2)e^{-ax}$
Since RHS is $e^{ax}$ and $m=a$ has multiplicity 3,
Particular integral = $x^3\frac{e^{ax}}{3!\,(2a)^3}
=\frac{x^2e^{ax}}{8a^2}$
Qus : 5
AMU MCA PYQ
4
The solution of the differential equation
$y\sin 2x,dx - (y^2 + \cos^2 x),dy = 0$ is:
1
$3y^2\cos 2x + 3y + 2y^3 = C$ 2
$3y^2\sin 2x + y^2 + 2y = C$ 3
$3y\cos 2x + 3y + 2y^3 = C$ 4
$3y\sin 2x + y^2 + 2y^3 = C$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2025 PYQ
Solution After making the equation exact and integrating, the solution obtained is
$3y\sin 2x + y^2 + 2y^3 = C$.
Qus : 6
AMU MCA PYQ
4
The solution of
$3\frac{\partial^2 z}{\partial x,\partial y} - 2\frac{\partial^2 z}{\partial y^2} - \frac{\partial z}{\partial y} = 0$ is:
1
$\phi_1(y) + e^{x/3}\phi_2(3y+2x)$ 2
$\phi_1(x) + e^{y/3}\phi_2(3y+2x)$ 3
$\phi_1(y) + e^{y/2}\phi_2(3y+2x)$ 4
$\phi_1(x) + e^{x/3}\phi_2(3y+2x)$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2025 PYQ
Solution Solving the auxiliary equation gives complementary function of the form
$\phi_1(x) + e^{x/3}\phi_2(3y+2x)$.
Qus : 9
AMU MCA PYQ
1
The extremal of functional
$\iint_D\left[\left(\frac{\partial z}{\partial x}\right)^2+\left(\frac{\partial z}{\partial y}\right)^2+\left(\frac{\partial^2 z}{\partial x\partial y}\right)^2\right]dxdy$
is
1
$Z=xF_1(y)+F_2(y)+yF_3(x)+F_4(x)$ 2
$Z=x^2F_1(y)+F_2(y)+y^2F_3(x)+F_4(x)$ 3
$Z=xF_1(y)+F_2(y)+y^2F_3(x)+F_4(x)$ 4
$Z=x^2F_1(y)+F_2(y)+yF_3(x)+F_4(x)$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2021 PYQ
Solution
Qus : 11
AMU MCA PYQ
1
The solution of the differential equation
$ \dfrac{d^2y}{dx^2} - 2\dfrac{dy}{dx} + y = xe^x \sin x $
1
$ y = (c_1 - c_2 x)e^x + e^x(2\cos x + x\sin x) $ 2
$ y = (c_1 + c_2 x)e^x - e^x(2\cos x + x\sin x) $ 3
$ y = (c_1 + c_2 x)e^{-x} - e^{-x}(2\cos x + x\sin x) $ 4
$ y = (c_1 + c_2 x)e^x + e^{-x}(2\cos x - x\sin x) $ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2021 PYQ
Solution Auxiliary equation:
$ m^2 - 2m + 1 = 0 $
$ (m-1)^2 = 0 $
So CF:
$ y_c = (c_1 + c_2 x)e^x $
Particular integral gives:
$ y_p = e^x(2\cos x + x\sin x) $
Therefore,
$ y = (c_1 + c_2 x)e^x + e^x(2\cos x + x\sin x) $
Qus : 14
AMU MCA PYQ
1
The general solution of $(y - z)p + (z - x)q = x - y$ is
1
$\phi(x + y + z,; x^2 + y^2 + z^2) = 0$ 2
$\phi(xyz,; x + y + z) = 0$ 3
$\phi(xyz,; x^2 + y^2 + z^2) = 0$ 4
$\phi(x^2 - y^2 - z^2,; x - y - z) = 0$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2020 PYQ
Solution Given Lagrange’s linear PDE
$(y - z)p + (z - x)q = x - y$
Auxiliary equations:
$\frac{dx}{y - z} = \frac{dy}{z - x} = \frac{dz}{x - y}$
First integral:
Add numerators and denominators:
$(y - z) + (z - x) + (x - y) = 0$
⇒ $dx + dy + dz = 0$
⇒ $x + y + z = c_1$
Second integral:
Multiply by $x, y, z$ respectively and add:
$x(y - z) + y(z - x) + z(x - y) = 0$
⇒ $d(x^2 + y^2 + z^2) = 0$
⇒ $x^2 + y^2 + z^2 = c_2$
Hence general solution is
$\phi(x + y + z,; x^2 + y^2 + z^2) = 0$
Qus : 15
AMU MCA PYQ
2
The solution of
$\frac{dx}{x^2 - yz - z^2} = \frac{dy}{2xy} = \frac{dz}{2xz}$
is given by
1
$\frac{y}{z} = c_1,; \frac{x^2 + y^2 - z^2}{z^2} = c_2$ 2
$\frac{y}{z} = c_1,; \frac{x^2 + y^2 - z^2}{2} = c_2$ 3
$\frac{z}{x} = c_1,; (x^2 + y^2 + z^2) = c_2$ 4
$\frac{y}{z} = c_1,; (x^2 + y^2 + z^2) = c_2$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2020 PYQ
Solution From second and third:
$\frac{dy}{2xy} = \frac{dz}{2xz}$
⇒ $\frac{dy}{y} = \frac{dz}{z}$
⇒ $\frac{y}{z} = c_1$
Using substitution in first part gives second integral
$\frac{x^2 + y^2 - z^2}{2} = c_2$
Qus : 16
AMU MCA PYQ
4
An integrating factor for
$(\cos y \sin 2x)dx + (\cos^2 y - \cos^2 x)dy = 0$
1
$\sec^2 y + \sec y \tan y$ 2
$\tan^2 y + \sec y \tan y$ 3
$\frac{1}{\sec^2 y + \sec y \tan y}$ 4
$\frac{1}{\tan^2 y + \sec y \tan y}$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2020 PYQ
Solution Using standard form and checking
$\frac{\partial M}{\partial y} - \frac{\partial N}{\partial x}$
Integrating factor becomes
$\frac{1}{\tan^2 y + \sec y \tan y}$
Qus : 17
AMU MCA PYQ
1
The general solution of $y = 2x \frac{dy}{dx} + y\left(\frac{dy}{dx}\right)^2$ is
1
$2xc - y + c^2 = 0$ 2
$2x^2c - y + c^2 = 0$ 3
$2xc - y^2 + c^2 = 0$ 4
$2x^2c - y^2 + c^2 = 0$ Go to Discussion
AMU MCA Previous Year PYQ
AMU MCA AMU MCA 2020 PYQ
Solution Put $p = \frac{dy}{dx}$
$y = 2xp + yp^2$
$y(1 - p^2) = 2xp$
$y = \frac{2xp}{1 - p^2}$
This is Clairaut’s form. Hence general solution is
$2xc - y + c^2 = 0$
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