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JNTU B.Tech I Year MATHEMATICS I Previous Question Paper (June - 2022 - R13)

B.Tech | I Year | I-I | R13 | June - 2022

Answer PaperPaper Code: 111ABMaximum Marks: 75Time: 3 Hours

Answer any five questions

All questions carry equal marks

Main

115 marks
a

Determine the rank of the matrix:

A = [[1, 3, 4, 3], [3, 9, 12, 3], [1, 3, 4, 1]]
7 marks

Answer

To find the rank of matrix A, we reduce it to row-echelon form using elementary row operations:

A = [[1, 3, 4, 3], [3, 9, 12, 3], [1, 3, 4, 1]]
  1. Perform R2 → R2 - 3R1 and R3 → R3 - R1:
  2. [[1, 3, 4, 3], [0, 0, 0, -6], [0, 0, 0, -2]]
  3. Perform R3 → R3 - (1/3)R2:
  4. [[1, 3, 4, 3], [0, 0, 0, -6], [0, 0, 0, 0]]

The number of non-zero rows in the row-echelon form is 2. Therefore, the rank of matrix A is 2.

b

Investigate the values of λ and μ so that the equations x + y + z = 2, x + 2y + 3z = 5, x + 3y + λz = μ have (i) no solution, (ii) a unique solution and (iii) an infinite number of solutions.

8 marks

Answer

The system of equations can be represented as an augmented matrix [A|B]:

[[1, 1, 1, 2], [1, 2, 3, 5], [1, 3, λ, μ]]

Applying row operations R2 → R2 - R1 and R3 → R3 - R1:

[[1, 1, 1, 2], [0, 1, 2, 3], [0, 2, λ-1, μ-2]]

Applying R3 → R3 - 2R2:

[[1, 1, 1, 2], [0, 1, 2, 3], [0, 0, λ-5, μ-8]]

Based on the final row:

  1. Unique solution: Occurs when the coefficient matrix is non-singular, i.e., λ - 5 ≠ 0. Thus, λ ≠ 5 and μ can be any value.
  2. No solution: Occurs when the rank of the coefficient matrix is less than the rank of the augmented matrix. This happens when λ - 5 = 0 and μ - 8 ≠ 0. Thus, λ = 5 and μ ≠ 8.
  3. Infinite solutions: Occurs when the rank of both matrices is equal and less than the number of variables. This happens when λ - 5 = 0 and μ - 8 = 0. Thus, λ = 5 and μ = 8.
2

Reduce the quadratic form 3x2 + 5y2 + 3z2 - 2yz + 2zx - 2xy to the canonical form and also write the nature of the quadratic matrix.

15 marks

Answer

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315 marks
a

State Rolle’s theorem and verify it for f(x) = ex sin x in [0, π].

7 marks

Answer

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b

If x = r cos θ, y = r sin θ then prove that

(∂(x, y) / ∂(r, θ)) × (∂(r, θ) / ∂(x, y)) = 1

8 marks

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415 marks
a

Prove that

B(m, n) = (Γ(m) Γ(n)) / Γ(m+n)

8 marks

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b

Evaluate

∫0∞ ∫0∞ e-(x2+y2) dx dy
by changing to polar coordinates.

7 marks

Answer

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515 marks
a

If a substance cools from 370 K to 330 K in 10 min., when the temperature of the surrounding air is 290 K, find the temperature of the substance after 40 min.

7 marks

Answer

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b

Solve (D2 - 3D + 2)y = cos 3x.

8 marks

Answer

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615 marks
a

Solve (D3 - 1)y = 4 cos 2x + ex.

8 marks

Answer

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b

Solve by method of variation of parameters (d2y / dx2) + 4y = tan 2x.

7 marks

Answer

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715 marks
a

Find L{(sin 3t cos t) / t} and L{t2 cos 2t}.

8 marks

Answer

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b

Find L-1{s2 / ((s2+4)(s2+9))} using Convolution theorem.

7 marks

Answer

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815 marks
a

(i) Find the Laplace Transform of L{t3 / (t+1)} and (ii) Find L{t e-t sin 2t}.

8 marks

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b

Solve the differential equation by Laplace transforms method: y'' + y' + y = t3, y(0) = 0, y'(0) = 1.

7 marks

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