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3 and 4 .Determinants and Matrices
medium
જો સમીકરણ સંહતિ
$x+y+a z=b$
$2 x+5 y+2 z=6$
$x+2 y+3 z=3$
ને અસંખ્ય ઉકેલો હોય, તો $2 a+3 b=.......$
A
$23$
B
$28$
C
$25$
D
$20$
(JEE MAIN-2023)
Solution
$\Delta=\left|\begin{array}{lll}1 & 1 & a \\ 2 & 5 & 2 \\ 1 & 2 & 3\end{array}\right|=0 \Rightarrow 11-4- a =0$
$a=7$
$\Delta_1=\left|\begin{array}{lll} b & 1 & a \\ 6 & 5 & 2 \\ 3 & 2 & 3\end{array}\right|=0 \Rightarrow 11 b -12-21=0$
$b =3$
$2 a+3 b=23$
Standard 12
Mathematics