The system of equations
\[
x+4y+6z=20,\qquad
x+y+z=6,\qquad
x+\lambda y+6z=20
\]
has
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Whenever a parameter appears in a system of linear equations, reduce the augmented matrix first. Then examine the special value(s) of the parameter separately to check whether the system is consistent, inconsistent, or has infinitely many solutions.