3 and 4 .Determinants and Matrices
easy

निम्नलिखित समीकरण से $x$ तथा $y$ के मानों को ज्ञात कीजिए:

$2\left[\begin{array}{cc}x & 5 \\ 7 & y-3\end{array}\right]+\left[\begin{array}{rr}3 & -4 \\ 1 & 2\end{array}\right]=\left[\begin{array}{rr}7 & 6 \\ 15 & 14\end{array}\right]$

A

$x=2$,   $y=9$

B

$x=2$,   $y=9$

C

$x=2$,   $y=9$

D

$x=2$,   $y=9$

Solution

$2\left[ {\begin{array}{*{20}{c}}
  x&5 \\ 
  7&{y – 3} 
\end{array}} \right] + \left[ {\begin{array}{*{20}{c}}
  3&{ – 4} \\ 
  1&2 
\end{array}} \right]$ $ = \left[ {\begin{array}{*{20}{c}}
  7&6 \\ 
  {15}&{14} 
\end{array}} \right] \Rightarrow $ $\left[ {\begin{array}{*{20}{c}}
  {2x}&{10} \\ 
  {14}&{2y – 6} 
\end{array}} \right] + $ $\left[ {\begin{array}{*{20}{c}}
  3&{ – 4} \\ 
  1&2 
\end{array}} \right] = \left[ {\begin{array}{*{20}{c}}
  7&6 \\ 
  {15}&{14} 
\end{array}} \right]$

or          $\left[ {\begin{array}{*{20}{c}}
  {2x + 3}&{10 – 4} \\ 
  {14 + 1}&{2y – 6 + 2} 
\end{array}} \right]$  $ = \left[ {\begin{array}{*{20}{c}}
  7&6 \\ 
  {15}&{14} 
\end{array}} \right] \Rightarrow $  $\left[ {\begin{array}{*{20}{c}}
  {2x + 3}&6 \\ 
  {15}&{2y – 4} 
\end{array}} \right]$ $ = \left[ {\begin{array}{*{20}{c}}
  7&6 \\ 
  {15}&{14} 
\end{array}} \right]$

or          $2 x+3=7$      and    $2 y-4=14$    (Why ?)

or          $2 x=7-3$      and    $2 y=18$

or          $x=\frac{4}{2}$      and    $y=\frac{18}{2}$

i.e.         $x=2$      and    $y=9$.

Standard 12
Mathematics

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