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JNTU B.Tech I MATHEMATICS-I Previous Question Paper (August - 2018 - R15)

B.Tech | I | I-I | R15 | August - 2018

Answer PaperPaper Code: 121ABMaximum Marks: 75Time: 3 hours

Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks and may have a, b, c as sub questions.

Part A

(25 Marks)

125 marks
a

A body is heated to 1100°C and placed in air at 100°C. After one hour its temperature is 600°C. How much additional time is required for it to cool to 300°C?

2 marks

Answer

Using Newton's Law of Cooling, T(t) = Ts + (T0 - Ts)e-kt. Given T0 = 1100, Ts = 100, and T(1) = 600, we have 600 = 100 + 1000e-k, so e-k = 0.5. For T(t) = 300, 300 = 100 + 1000e-kt, so e-kt = 0.2 = (0.5)log0.5(0.2). Since e-k = 0.5, then t = log0.5(0.2) ≈ 2.32 hours. The additional time required is 2.32 - 1 = 1.32 hours.

b

Find the integrating factor for the following equation:

(3xy - 2ay^2)dx + (x^2 - 2axy)dy = 0

3 marks

Answer

The equation is Mdx + Ndy = 0 with M = 3xy - 2ay2 and N = x2 - 2axy. Here, ∂M/∂y = 3x - 4ay and ∂N/∂x = 2x - 2ay. Since (∂M/∂y - ∂N/∂x)/N = (x - 2ay)/(x2 - 2axy) = 1/x, the integrating factor is e∫(1/x)dx = eln(x) = x.

c

Find the rank of the matrix:

[[1, -2, 3, -1], [2, -1, 2, 2], [3, 1, 2, 3]]

2 marks

Answer

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d

Find the value of x such that the Rank of the following matrix is 2:

[[4, 2, 5, 0], [2, 5, 4, 5], [0, 5, x, 0]]

3 marks

Answer

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e

Find the sum and product of Eigen values of A =

[[8, -1], [2, 2]]

2 marks

Answer

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f

If 1, 3, -2 are eigen values of a matrix A, then find the eigen values of 2A+3I.

3 marks

Answer

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g

Write the Taylor’s series expansion for f(x,y) about the point (a,b).

2 marks

Answer

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h

Find the value of ∂^3u / ∂x∂y∂z, where u = x^3 y^3 z^3

3 marks

Answer

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i

Form the partial differential equation of z = ax^2 + by^2 where a and b are arbitrary constants.

2 marks

Answer

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j

Find the order and degree of the partial differential equation:

(∂^2z/∂x^2)^2 + (∂^2z/∂y^2)^2 = 5

3 marks

Answer

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Part B

(50 Marks)

210 marks
a

Solve the differential equation (D^2 - 1)y = x^2e^x.

5 marks

Answer

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b

Find the orthogonal trajectories of the lines y = mx, m is arbitrary constant.

5 marks

Answer

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OR
310 marks
a

Solve the differential equation (D^2 - 5D + 6)y = Sin 4x.

5 marks

Answer

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b

In a culture of yeast, the active ferment doubles itself in 3 hours. Determine the number of times it multiplies itself in 15 hours.

5 marks

Answer

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410 marks
a

Find the eigen values and eigen vectors of the matrix:

[[3, -1, 1], [-1, 5, -1], [1, -1, 3]]

5 marks

Answer

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b

Find by LU decomposition method solve the linear system:

[[-3, 12, -6], [1, -2, 2], [0, 1, 1]] [x, y, z]^T = [-33, 7, -1]^T

5 marks

Answer

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OR
510 marks
a

Find the value of k for which the system of equations (k+1)x + 8y = 4k; kx + (k-3)y = 3k-1 has infinitely many solutions.

5 marks

Answer

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b

Solve the system of equations by the Gauss Seidel method: 10x + y + z = 12, 2x + 10y + z = 13, 2x + 2y + 10z = 14

5 marks

Answer

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610 marks
a

If a matrix A = [[-1, 0, 0], [2, -3, 0], [1, 4, 2]], then find the Eigen values of A^2?

5 marks

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b

If A = [[1, 2, -3], [0, 3, 2], [0, 0, -2]], then find eigenvalues of 3A^3 + 5A^2 - 6A - 2I.

5 marks

Answer

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OR
710 marks
a

Reduce the quadratic form 6x1^2 + 3x2^2 + 3x3^2 - 4x1x2 - 2x3x2 + 4x3x1 to canonical form.

5 marks

Answer

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b

If λ is an eigenvalue of A, then prove that λ^m is an eigenvalue of A^m (m is any positive integer).

5 marks

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810 marks
a

If u = x log(xy) where x^3 + y^3 + 3xy = 1, find the value of du/dx.

5 marks

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b

Find the Taylor’s series expansion of f(x, y) = Sin(xy) about the point (0, π).

5 marks

Answer

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OR
910 marks
a

Find the maximum and minimum values of the function f(x, y, z) = 2x + 3y + z, under the conditions x^2 + y^2 = 5 and x + y = 1.

5 marks

Answer

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b

The sum of three positive numbers is constant. For what values of x, y and z is their product a maximum?

5 marks

Answer

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1010 marks
a

If p = ∂z/∂x and q = ∂z/∂y, solve: p - q = log(x + y).

5 marks

Answer

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b

If p = ∂z/∂x and q = ∂z/∂y, solve: y^2p - xyq = x(z - 2y).

5 marks

Answer

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OR
1110 marks
a

If p = ∂z/∂x and q = ∂z/∂y, solve: p = log(px - y).

5 marks

Answer

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b

If p = ∂z/∂x and q = ∂z/∂y, solve: p - x^2 = q + y^2.

5 marks

Answer

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About this paper

This page contains the question paper of MATHEMATICS-I from JNTU for B.Tech ECE I I-I, August - 2018, R15.

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