NDA & NA Exam (I)- 2017 - Mathematics Defence Question Paper

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NDA & NA Exam (I)- 2017 - Mathematics

NDA & NA Exam (I)- 2017 - Mathematics Defence Questions

11.
The modulus and principal argument of the complex number \( \frac{1 + 2i}{1 - (1 - i)^{2}} \) are respectively
A.
1, 0
B.
1, 1
C.
2, 0
D.
2, 1
ANSWER :
A. 1, 0
12.
If the graph of a quadratic polynomial lies entirely above x-axis, then which one of the following is correct?
A.
Both the roots are real
B.
One root is real and the other is complex
C.
Both the roots are complex
D.
Cannot say
ANSWER :
C. Both the roots are complex
13.
If \( |z + 4| \leq 3 \), then the maximum value of \( |z + 1| \) is
A.
0
B.
4
C.
6
D.
10
ANSWER :
C. 6
14.
The number of roots of the equation \( z^{2} = 2\bar{z} \) is
A.
2
B.
3
C.
4
D.
zero
ANSWER :
C. 4
15.
If \( \cot\alpha \) and \( \cot\beta \) are the roots of the equation \( x^{2} + bx + c = 0 \) with \( b \neq 0 \), then the value of \( \cot(\alpha + \beta) \) is
A.
\( \frac{c-1}{b} \)
B.
\( \frac{1-c}{b} \)
C.
\( \frac{b}{c-1} \)
D.
\( \frac{b}{1-c} \)
ANSWER :
B. \( \frac{1-c}{b} \)
16.
The sum of the roots of the equation \( x^{2} + bx + c = 0 \) (where b and c are non-zero) is equal to the sum of the reciprocals of their squares. Then \( \frac{1}{c} \), b, \( \frac{c}{b} \) are in
A.
AP
B.
GP
C.
HP
D.
None of the above
ANSWER :
C. HP
17.
The sum of the roots of the equation \( ax^{2} + x + c = 0 \) (where a and c are non-zero) is equal to the sum of the reciprocals of their squares. Then a, \( ca^{2} \), \( c^{2} \) are in
A.
AP
B.
GP
C.
HP
D.
None of the above
ANSWER :
A. AP
18.
The value of [C(7, 0) + C(7, 1)] + [C(7, 1) + C(7, 2)] + … + [C(7, 6) + C(7, 7)] is
A.
254
B.
255
C.
256
D.
257
ANSWER :
A. 254
19.
The number of different words (eight-letter words) ending and beginning with a consonant which can be made out of the letters of the word β€˜EQUATION’ is
A.
5200
B.
4320
C.
3000
D.
2160
ANSWER :
B. 4320
20.
The fifth term of an AP of n terms, whose sum is \( n^{2} - 2n \), is
A.
5
B.
7
C.
8
D.
15
ANSWER :
B. 7