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3 and 4 .Determinants and Matrices
medium
If the system of equations $k x+y+2 z=1$ ; $3 x-y-2 z=2$ ; $-2 x-2 y-4 z=3$ has infinitely many solutions, then $k$ is equal to ..........
A
$21$
B
$42$
C
$14$
D
$28$
(JEE MAIN-2021)
Solution
We observe $5 P _{2}- P _{1}=3 P _{3}$
So, $15- K =-6$
$\Rightarrow K =21$
Standard 12
Mathematics