MCQ
The system of equations
$
\begin{array}{l}
x+y+z=6 \\
x+2 y+5 z=9 \\
x+5 y+\lambda z=\mu
\end{array}
$
has no solution if
  • $\lambda=17, \mu \neq 18$
  • B
    $\lambda \neq 17, \mu \neq 18$
  • C
    $\lambda=15, \mu \neq 17$
  • D
    $\lambda=17, \mu=18$

Answer

Correct option: A.
$\lambda=17, \mu \neq 18$
(A)
$
\begin{array}{l}
D=\left|\begin{array}{lll}
1 & 1 & 1 \\
1 & 2 & 5 \\
1 & 5 & \lambda
\end{array}\right|=0 \\
\lambda=17 \\
D_z=\left|\begin{array}{lll}
1 & 1 & 6 \\
1 & 2 & 9 \\
1 & 5 & \mu
\end{array}\right| \neq 0 \\
\mu \neq 18
\end{array}
$

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