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3 and 4 .Determinants and Matrices
medium
क्रमित युग्म $( a , b )$ जिसके लिये रेखीय समीकरण
निकाय
$3 x -2 y + z = b$
$5 x -8 y +9 z =3$
$2 x + y + az =-1$
का कोई हल नहीं है, होगा:
A
$\left(3, \frac{1}{3}\right)$
B
$\left(-3, \frac{1}{3}\right)$
C
$\left(-3,-\frac{1}{3}\right)$
D
$\left(3,-\frac{1}{3}\right)$
(JEE MAIN-2022)
Solution
$\left|\begin{array}{ccc} 3 & -2 & 1 \\ 5 & -8 & 9 \\ 2 & 1 & a \end{array}\right|=0$
$3(-8 a-9)+2(5 a-18)+1(21)=0$
$\Rightarrow a=-3$
Also $\Delta_{2}=\left|\begin{array}{ccc}3 & -2 & b^{\frac{1}{3}} \\ 5 & 8 & 3 \\ 2 & 1 & -1\end{array}\right|$
If $b =\frac{1}{3}$
$\Delta_{2}=0$
So $b$ must be equal to $-\frac{1}{3}$
Standard 12
Mathematics