NDA & NA Exam (I)- 2019 - Mathematics Defence Question Paper

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NDA & NA Exam (I)- 2019 - Mathematics

NDA & NA Exam (I)- 2019 - Mathematics Defence Questions

1.
What is the nth term of the sequence 25, −125, 625, −3125, ...?
A.
\( (5)^{n+1} \)
B.
\( (-1)^{2n} 5^{n+1} \)
C.
\( (-1)^{2n-1} 5^{n+1} \)
D.
\( (-1)^{n-1} 5^{n+1} \)
ANSWER :
D. \( (-1)^{n-1} 5^{n+1} \)
2.
Suppose \( X = \{1, 2, 3, 4\} \) and R is a relation on X. If \( R = \{(1, 1), (2, 2), (3, 3), (1, 2), (2, 1), (2, 3), (3, 2)\} \), then which one of the following is correct?
A.
R is reflexive and symmetric, but not transitive
B.
R is symmetric and transitive, but not reflexive
C.
R is reflexive and transitive, but not symmetric
D.
R is neither reflexive nor transitive, but symmetric
ANSWER :
D. R is neither reflexive nor transitive, but symmetric
3.
A relation R is defined on the set N of natural numbers as \( xRy \Rightarrow x^{2} - 4xy + 3y^{2} = 0 \). Then which one of the following is correct?
A.
R is reflexive and symmetric, but not transitive
B.
R is reflexive and transitive, but not symmetric
C.
R is reflexive, symmetric and transitive
D.
R is reflexive, but neither symmetric nor transitive
ANSWER :
D. R is reflexive, but neither symmetric nor transitive
4.
If \( A = \{x \in Z : x^{3} - 1 = 0\} \) and \( B = \{x \in Z : x^{2} + x + 1 = 0\} \), where Z is set of complex numbers, then what is \( A \cap B \) equal to?
A.
Null set
B.
\( \left\{ \frac{-1 + \sqrt{3}i}{2}, \frac{-1 - \sqrt{3}i}{2} \right\} \)
C.
\( \left\{ \frac{-1 + \sqrt{3}i}{4}, \frac{-1 - \sqrt{3}i}{4} \right\} \)
D.
\( \left\{ \frac{1 + \sqrt{3}i}{2}, \frac{1 - \sqrt{3}i}{2} \right\} \)
ANSWER :
B. \( \left\{ \frac{-1 + \sqrt{3}i}{2}, \frac{-1 - \sqrt{3}i}{2} \right\} \)
5.
Consider the following statements for the two non-empty sets A and B:
1. \( (A \cap B) \cup (A \cap \bar{B}) \cup (\bar{A} \cap B) = A \cup B \)
2. \( A \cup (\bar{A} \cap B) = A \cup B \)
Which of the above statements is/are correct?
A.
1 only
B.
2 only
C.
Both 1 and 2
D.
Neither 1 nor 2
ANSWER :
C. Both 1 and 2
6.
Let X be a non-empty set and let A, B, C be subsets of X. Consider the following statements:
1. \( A \subseteq C \Rightarrow (A \cap B) \subseteq (C \cap B), (A \cup B) \subseteq (C \cup B) \)
2. \( (A \cap B) \subseteq (C \cap B) \) for all sets \( B \Rightarrow A \subseteq C \)
3. \( (A \cup B) \subseteq (C \cup B) \) for all sets \( B \Rightarrow A \subseteq C \)
Which of the above statements are correct?
A.
1 and 2 only
B.
2 and 3 only
C.
1 and 3 only
D.
1, 2 and 3
ANSWER :
D. 1, 2 and 3
7.
If \( B = \begin{bmatrix} 3 & 2 & 0 \\ 2 & 4 & 0 \\ 1 & 1 & 0 \end{bmatrix} \), then what is adjoint of B equal to?
A.
\( \begin{bmatrix} 0 & 0 & 0 \\ 0 & 0 & 0 \\ -2 & -1 & 8 \end{bmatrix} \)
B.
\( \begin{bmatrix} 0 & 0 & -2 \\ 0 & 0 & -1 \\ 0 & 0 & 8 \end{bmatrix} \)
C.
\( \begin{bmatrix} 0 & 0 & 2 \\ 0 & 0 & 1 \\ 0 & 0 & 0 \end{bmatrix} \)
D.
It does not exist
ANSWER :
A. \( \begin{bmatrix} 0 & 0 & 0 \\ 0 & 0 & 0 \\ -2 & -1 & 8 \end{bmatrix} \)
8.
What are the roots of the equation \( \left| x^{2} - x - 6 \right| = x + 2 \)?
A.
−2, 1, 4
B.
0, 2, 4
C.
0, 1, 4
D.
−2, 2, 4
ANSWER :
D. −2, 2, 4
9.
If \( A = \begin{bmatrix} 0 & 1 \\ 1 & 0 \end{bmatrix} \), then the matrix A is a/an
A.
Singular matrix
B.
Involutory matrix
C.
Nilpotent matrix
D.
Idempotent matrix
ANSWER :
B. Involutory matrix
10.
If \( \begin{vmatrix} x & -3i & 1 \\ y & 1 & i \\ 0 & 2i & -i \end{vmatrix} = 6 + 11i \), then what are the values of x and y respectively?
A.
−3, 4
B.
3, 4
C.
3, −4
D.
−3, −4
ANSWER :
A. −3, 4