Question

If \[A = \left[ {\begin{array}{*{20}{c}} 1&2\\ 3&5 \end{array}} \right],\]   then the value of the determinant $$\left| {{A^{2009}} - 5{A^{2008}}} \right|$$    is

A. $$ - 6$$  
B. $$ - 5$$
C. $$ - 4$$
D. $$4$$
Answer :   $$ - 6$$
Solution :
Given, \[A = \left[ {\begin{array}{*{20}{c}} 1&2\\ 3&5 \end{array}} \right]\]
$$\eqalign{ & \Rightarrow \left| A \right| = 5 - 6 = - 1 \cr & \therefore \left| {{A^{2009}} - 5{A^{2008}}} \right| = \left| {{A^{2008}}} \right|\left| {A - 5I} \right| \cr} $$
\[ = {\left( { - 1} \right)^{2008}}\left| {\left[ {\begin{array}{*{20}{c}} 1&2\\ 3&5 \end{array}} \right] - \left[ {\begin{array}{*{20}{c}} 5&0\\ 0&5 \end{array}} \right]} \right| = \left| {\begin{array}{*{20}{c}} { - 4}&2\\ 3&0 \end{array}} \right| = - 6\]

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. $$AB=BA$$

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