Gujarati
Hindi
3 and 4 .Determinants and Matrices
medium

Let $A + 2B =$ $\left[ {\begin{array}{*{20}{c}}1&2&0\\6&{ - 3}&3\\{ - 5}&3&1 \end{array}} \right]$ and $2A - B =$ $\left[ {\begin{array}{*{20}{c}}2&{ - 1}&5\\ 2&{ - 1}&6\\0&1&2\end{array}} \right]$ then $Tr (A) - Tr (B)$ has the value equal to

A

$0$

B

$1$

C

$2$

D

none

Solution

$t_r(A) + 2 t_r(B) = – 1$ (from the given matrix)
and $2 t_r(A) – t_r(B) = 3$ (from the given matrix)
Let $t_r(A) = x$ and $t_r(B) = y$
      $x + 2y = – 1$
      $2x – y = 3$
solving $x = 1$ and $y = – 1$
Hence $t_r(A) – t_r(B) = x – y = 2$

Standard 12
Mathematics

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