3 and 4 .Determinants and Matrices
medium

यदि $A = \left[ {\begin{array}{*{20}{c}}{ab}&{{b^2}}\\{ - {a^2}}&{ - ab}\end{array}} \right]$ और ${A^n} = O$, तो $n$ का न्यूनतम मान है

A

$2$

B

$3$

C

$4$

D

$5$

Solution

(a) ${A^2} = A.\,\,A = \left[ {\begin{array}{*{20}{c}}{ab}&{{b^2}}\\{ – {a^2}}&{ – ab}\end{array}} \right]\,\left[ {\begin{array}{*{20}{c}}{ab}&{{b^2}}\\{ – {a^2}}&{ – ab}\end{array}} \right]$

$ = \left[ {\begin{array}{*{20}{c}}{{a^2}{b^2} – {a^2}{b^2}}&{a{b^3} – a{b^3}}\\{ – {a^3}b + {a^3}b}&{ – {a^2}{b^2} + {a^2}{b^2}}\end{array}} \right] = O$

$ \Rightarrow \,\,{A^3} = A.{A^2} = 0$ व ${A^n} = 0$,$n \ge 2$ के प्रत्येक मान के लिए।

 

Standard 12
Mathematics

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