3 and 4 .Determinants and Matrices
hard

यदि रैखिक समीकरण निकाय $x-2 y+k z=1$, $2 x+y+z=2$, $3 x-y-k z=3$ का एक हल $( x , y , z ), z \neq 0$, है, तो $( x , y )$ जिस रेखा पर स्थित है, उसका समीकरण है

A

$3x -4y -1 = 0$

B

$4x -3y -4 = 0$

C

$4x -3y -1 = 0$

D

$3x -4y -4 = 0$

(JEE MAIN-2019)

Solution

For infinitly many solution 

$\left| {\begin{array}{*{20}{c}}
1&{ – 2}&k\\
2&1&1\\
3&{ – 1}&{ – k}
\end{array}} \right| – 0$

$ \Rightarrow k = \frac{{ – 1}}{2}$

Also consider 

$x – 2y + k = 1$ and $2x + y + z = 2$

$ \Rightarrow 2x – 4y – z – 2$  

      $2x + y + z = 2$

$ \Rightarrow 4x – 3y = 4$

Standard 12
Mathematics

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