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3 and 4 .Determinants and Matrices
easy
If $3X + 2Y = I$ and $2X - Y = O$, where $ I $ and $O$ are unit and null matrices of order $3$ respectively, then
A
$X = (1/7),Y = (2/7)$
B
$X = (2/7),Y = (1/7)$
C
$X = (1/7)I,Y = (2/7)\,I$
D
$X = (2/7)\,I,Y = (1/7)\,I$
Solution
(c) $\begin{array}{l}3X + 2Y = I\\2X – Y = O\end{array}$ $ \Rightarrow $ $\begin{array}{l}3X + 2Y = I\\4X – 2Y = O\end{array}$ $ \Rightarrow $ $\begin{array}{l}7X = I\\\,\,X = \frac{1}{7}I\end{array}$ (एक साथ हल करने पर)
अत: समीकरण $(i)$ से $(i),$ $2Y = I – \frac{3}{7}I = \frac{4}{7}I \Rightarrow Y = \frac{2}{7}I$.
Standard 12
Mathematics