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STD 12 - 3 and 4 . determinant and metrices — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEESTD 12 - 3 and 4 . determinant and metrices4 Marks
Question
If $A = \left[ {\begin{array}{*{20}{c}}{1/3}&2\\0&{2x - 3}\end{array}} \right],B = \left[ {\begin{array}{*{20}{c}}3&6\\0&{ - 1}\end{array}} \right]$and $AB = I$, then $x =$
✓

Answer

b
(b) $\left[ {\begin{array}{*{20}{c}}
  {1/3}&2 \\ 
  0&{2x - 3} 
\end{array}} \right]\left[ {\begin{array}{*{20}{c}}
  3&6 \\ 
  0&{ - 1} 
\end{array}} \right] = \left[ {\begin{array}{*{20}{c}}
  1&0 \\ 
  0&{3 - 2x} 
\end{array}} \right] = I = \left[ {\begin{array}{*{20}{c}}
  1&0 \\ 
  0&1 
\end{array}} \right]$

(As given)

$\Leftrightarrow \,\,3 - 2x = 1$ or $x = 1$.

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