Question:medium

The set of values of \(k\) for which the system of simultaneous equations \[ x+y+kz = 1, \quad 2x+2y-3, \quad x+2y+2kz = k \] has no real solution is:

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For simultaneous equations, identify parameters which eliminate variables causing inconsistency; those values correspond to no real solution.
Updated On: Jul 18, 2026
  • \(\{0\}\)
  • \(\mathbb{R} - \{0\}\)
  • \(\{2\}\)
  • \(\{-1,0,1\}\)
Show Solution

The Correct Option is A

Solution and Explanation

Step 1: Use the second equation to pin down x+y directly.
The system is \(x+y+kz=1\), \(2x+2y-3=0\), and \(x+2y+2kz=k\).
From the second equation, \(2x+2y=3\), so \(x+y=\frac{3}{2}\).

Step 2: Substitute into the first equation.
\(x+y+kz=1 \Rightarrow \frac{3}{2}+kz=1 \Rightarrow kz=-\frac{1}{2}\)
This single relation decides everything: if \(k\neq 0\), it fixes \(z=-\frac{1}{2k}\); but if \(k=0\), it demands \(0=-\frac{1}{2}\), which is impossible.

Step 3: Confirm a real solution exists whenever k is not zero.
With \(z=-\frac{1}{2k}\), the third equation gives \(x+2y+2kz=k \Rightarrow x+2y-1=k \Rightarrow x+2y=k+1\).
Solving this together with \(x+y=\frac{3}{2}\) gives \(y=k-\frac{1}{2}\) and \(x=2-k\), a genuine solution for every \(k\neq 0\).

Step 4: Conclusion.
Only \(k=0\) breaks the system, so
\[ \boxed{\{0\}} \]
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