Question

Let $$A, B , C, D$$   be (not necessarily square) real matrices such that $$A^T = BCD; B^T = CDA; C^T = DAB$$        and $$DT = ABC$$   for the matrix $$S = ABCD, S^3 =$$

A. $$I$$
B. $$S^2$$
C. $$S$$  
D. $$O$$
Answer :   $$S$$
Solution :
$$\eqalign{ & S = ABCD = A\left( {BCD} \right) = A{A^T}\,\,\,\,.....\left( 1 \right) \cr & {S^3} = \left( {ABCD} \right)\left( {ABCD} \right)\left( {ABCD} \right) \cr & = \left( {ABC} \right)\left( {DAB} \right)\left( {CDA} \right)\left( {BCD} \right) \cr & = {D^T}{C^T}{B^T}{A^T} \cr & = {\left( {BCD} \right)^T}{A^T} = A{A^T}\,\,\,\,\,\,\,.....\left( 2 \right) \cr} $$
From (1) and (2), $$S = {S^3}$$

Releted MCQ Question on
Algebra >> Matrices and Determinants

Releted Question 1

Consider the set $$A$$ of all determinants of order 3 with entries 0 or 1 only. Let $$B$$  be the subset of $$A$$ consisting of all determinants with value 1. Let $$C$$  be the subset of $$A$$ consisting of all determinants with value $$- 1.$$ Then

A. $$C$$ is empty
B. $$B$$  has as many elements as $$C$$
C. $$A = B \cup C$$
D. $$B$$  has twice as many elements as elements as $$C$$
Releted Question 2

If $$\omega \left( { \ne 1} \right)$$  is a cube root of unity, then
\[\left| {\begin{array}{*{20}{c}} 1&{1 + i + {\omega ^2}}&{{\omega ^2}}\\ {1 - i}&{ - 1}&{{\omega ^2} - 1}\\ { - i}&{ - i + \omega - 1}&{ - 1} \end{array}} \right|=\]

A. 0
B. 1
C. $$i$$
D. $$\omega $$
Releted Question 3

Let $$a, b, c$$  be the real numbers. Then following system of equations in $$x, y$$  and $$z$$
$$\frac{{{x^2}}}{{{a^2}}} + \frac{{{y^2}}}{{{b^2}}} - \frac{{{z^2}}}{{{c^2}}} = 1,$$    $$\frac{{{x^2}}}{{{a^2}}} - \frac{{{y^2}}}{{{b^2}}} + \frac{{{z^2}}}{{{c^2}}} = 1,$$    $$ - \frac{{{x^2}}}{{{a^2}}} + \frac{{{y^2}}}{{{b^2}}} + \frac{{{z^2}}}{{{c^2}}} = 1$$     has

A. no solution
B. unique solution
C. infinitely many solutions
D. finitely many solutions
Releted Question 4

If $$A$$ and $$B$$ are square matrices of equal degree, then which one is correct among the followings?

A. $$A + B = B + A$$
B. $$A + B = A - B$$
C. $$A - B = B - A$$
D. $$AB=BA$$

Practice More Releted MCQ Question on
Matrices and Determinants


Practice More MCQ Question on Maths Section