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3 and 4 .Determinants and Matrices
normal
ધારોકે $S$ એ $\lambda$ ની એવી કિંમતોનો ગણ છે, જેના માટે સમીકરણ સંહિત
$6 \lambda x-3 y+3 z=4 \lambda^2$
$2 x+6 \lambda y+4 z=1$
$3 x+2 y+3 \lambda z=\lambda$
ને ઉકેલ નથી. તો $12 \sum_{\lambda \in S}|\lambda|=........$
A
$23$
B
$22$
C
$24$
D
$21$
(JEE MAIN-2023)
Solution
$\Delta=\left|\begin{array}{ccc}6 \lambda & -3 & 3 \\ 2 & 6 \lambda & 4 \\ 3 & 2 & 3 \lambda\end{array}\right|=0$ (For No Solution)
$2 \lambda\left(9 \lambda^2-4\right)+(3 \lambda-6)+(2-9 \lambda)=0$
$18 \lambda^3-14 \lambda-4=0$
$(\lambda-1)(3 \lambda+1)(3 \lambda+2)=0$
$\Rightarrow \lambda=1,-1 / 3,-2 / 3$
For each $\lambda, \Delta_1=\left|\begin{array}{ccc}6 \lambda & -3 & 4 \lambda^2 \\ 2 & 6 \lambda & 1 \\ 3 & 2 & \lambda\end{array}\right| \neq 0$
Ans. $12\left(1+\frac{1}{3}+\frac{2}{3}\right)=24$
Standard 12
Mathematics