1
NDA 2015 Paper 2
MCQ (Single Correct Answer)
+2.5
-0.83
If $$A = \left[ {\matrix{ 2 & 7 \cr 1 & 5 \cr } } \right]$$, then what is $$A + 3{A^{ - 1}}$$ equal to?

where, I is the identity matrix of order 2.
A
3I
B
5I
C
7I
D
None of these
2
NDA 2015 Paper 2
MCQ (Single Correct Answer)
+2.5
-0.83
The matrix $$\left[ {\matrix{ 0 & { - 4 + i} \cr {4 + i} & 0 \cr } } \right]$$ is
A
symmetric
B
skew-symmetric
C
hermitian
D
skew-hermitian
3
NDA 2015 Paper 2
MCQ (Single Correct Answer)
+2.5
-0.83
If $$X = \left[ {\matrix{ 3 & { - 4} \cr 1 & { - 1} \cr } } \right]$$, $$B = \left[ {\matrix{ 5 & 2 \cr { - 2} & 1 \cr } } \right]$$ and $$A = \left[ {\matrix{ p & q \cr r & s \cr } } \right]$$ satisfy the equation AX = B, then the matrix A is equal to
A
$$\left[ {\matrix{ 7 & {26} \cr 1 & { - 5} \cr } } \right]$$
B
$$\left[ {\matrix{ 7 & {26} \cr 4 & {17} \cr } } \right]$$
C
$$\left[ {\matrix{ { - 7} & { - 4} \cr {26} & {13} \cr } } \right]$$
D
$$\left[ {\matrix{ { - 7} & { - 26} \cr { - 6} & {23} \cr } } \right]$$
4
NDA 2015 Paper 2
MCQ (Single Correct Answer)
+2.5
-0.83
Let $$A = \left[ {\matrix{ {x + y} & y \cr {2x} & {x - y} \cr } } \right]$$, $$B = \left[ {\matrix{ 2 \cr { - 1} \cr } } \right]$$ and $$C = \left[ {\matrix{ 3 \cr 2 \cr } } \right]$$. If AB = C, then what is A2 equal to?
A
$$\left[ {\matrix{ 6 & { - 10} \cr 4 & {26} \cr } } \right]$$
B
$$\left[ {\matrix{ { - 10} & 5 \cr 4 & {24} \cr } } \right]$$
C
$$\left[ {\matrix{ { - 5} & { - 6} \cr { - 4} & { - 20} \cr } } \right]$$
D
$$\left[ {\matrix{ { - 5} & { - 7} \cr { - 5} & {20} \cr } } \right]$$
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