1
NDA 2015 Paper 2
MCQ (Single Correct Answer)
+2.5
-0.83
If A is an orthogonal matrix of order 3 and $$B = \left[ {\matrix{ 1 & 2 & 3 \cr { - 3} & 0 & 2 \cr 2 & 5 & 0 \cr } } \right]$$, then which of the following is/are correct?

1. $$\left| {AB} \right| = \pm \,47$$ 2. AB = BA

Select the correct answer using the code given below.
A
Only 1
B
Only 2
C
Both 1 and 2
D
Neither 1 nor 2
2
NDA 2016 Paper 2
MCQ (Single Correct Answer)
+2.5
-0.83
If $$A = \left[ {\matrix{ 1 & { - 1} \cr 2 & 3 \cr } } \right]$$ and $$B = \left[ {\matrix{ 2 & 3 \cr { - 1} & { - 2} \cr } } \right]$$, then which of the following is/are correct?

I. AB (A$$-$$1 B$$-$$1) is a unit matrix.

II. (AB)$$-$$1 = A$$-$$1 B$$-$$1.

Select the correct answer using the code given below.
A
Only I
B
Only II
C
Both I and II
D
Neither I nor II
3
NDA 2016 Paper 1
MCQ (Single Correct Answer)
+2.5
-0.83
Consider the following in respect of the matrix $$A = \left[ {\matrix{ { - 1} & 1 \cr 1 & { - 1} \cr } } \right]$$

1. A2 = $$-$$ A

2. A3 = 4A

Which of the above is/are correct?
A
Only 1
B
Only 2
C
Both 1 and 2
D
Neither 1 nor 2
4
NDA 2017 Paper 2
MCQ (Single Correct Answer)
+2.5
-0.83
If $$A = \left( {\matrix{ { - 2} & 2 \cr 2 & { - 2} \cr } } \right)$$, then which one of the following is correct?
A
$${A^2} = - 2A$$
B
$${A^2} = - 4A$$
C
$${A^2} = - 3A$$
D
$${A^2} = 4A$$
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