Mathematics (NDA/NA SOLVED PAPER 2019 (I) (01 to 50)

Total Questions: 50

21. What is the number of terms in the expansion of [(2x - 3y)² (2x + 3y)²]²?

Correct Answer: (b) 5
Solution:

Given, [(2x - 3y)² (2x + 3y)²]²
= [4x² - 9y²]⁴
∴ Total number of terms = 4 + 1 = 5

22. In the expansion of (1 +ax)ⁿ, the first three terms are respectively 1,12x and 64x². What is n equal to?

Correct Answer: (b) 9
Solution:

23. The numbers 1, 5 and 25 can be three terms (not necessarily consecutive) of:

Correct Answer: (d) finite number of GPs
Solution:

We have, 1, 5, 25 be three terms. Clearly, 1, 5, 25 are finite number of GPs.

24. The sum of (p + q)th and (p - q)th terms of an AP is equal to

Correct Answer: (c) twice the p th term
Solution:

25. If A is a square matrix of order n > 1, then which one of the following is correct?

Correct Answer: (b) det (-A) = (-1)ⁿ det A
Solution:

26. What is the least value of 25 cosec²x + 36 sec²x?

Correct Answer: (d) 121
Solution:

27. Question:- (27 to 28): Read the information carefully and answer the given questions.

What is det (2AB) equal to?
Let A and B be 3 × 3  matrices with det A = 4 and det B = 3 .

Correct Answer: (a) 96
Solution:

28. What is det (3 AB⁻¹) equal to?

Let A and B be 3 × 3  matrices with det A = 4 and det B = 3 .

Correct Answer: (c) 36
Solution:

29. Question:- (29 to 30) : Read the information carefully and answer the given questions. A complex number is given by:

What is the modulus of z?

Correct Answer: (c) 1
Solution:

30. What is the principal argument of z?

Correct Answer: (a) 0
Solution: