3 and 4 .Determinants and Matrices
medium

જો $A =\left[\begin{array}{ll} a & b \\ c & d \end{array}\right]$ અને $B =\left[\begin{array}{l}\alpha \\ \beta\end{array}\right] \neq\left[\begin{array}{l}0 \\ 0\end{array}\right]$ છે કે જેથી $AB = B$ અને $a + d =2021,$ તો $ad - bc$ ની કિમંત મેળવો.

A

$1010$

B

$1560$

C

$2250$

D

$2020$

(JEE MAIN-2021)

Solution

$A =\left[\begin{array}{ll} a & b \\ c & d \end{array}\right], B =\left[\begin{array}{l}\alpha \\ \beta\end{array}\right]$

$AB = B$

$\Rightarrow( A – I ) B = O$

$\Rightarrow| A – I |= O ,$ since $B \neq O$

$\left|\begin{array}{cc}( a -1) & b \\ c & ( d -1)\end{array}\right|=0$

$ad – bc =2020$

Standard 12
Mathematics

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