Concept:
• Centre of circle is midpoint of diameter
Step 1: Find centre
\[
x^2 + y^2 + 3x + y - 6 = 0
\]
\[
\text{Centre} = \left(-\frac{3}{2}, -\frac{1}{2}\right)
\]
Step 2: Use midpoint formula
Let other end be $(x,y)$
\[
\left(\frac{x-4}{2}, \frac{y-2}{2}\right) = \left(-\frac{3}{2}, -\frac{1}{2}\right)
\]
Step 3: Solve equations
\[
\frac{x-4}{2} = -\frac{3}{2} \Rightarrow x = 1
\]
\[
\frac{y-2}{2} = -\frac{1}{2} \Rightarrow y = 1
\]
Final Conclusion:
\[
(1,1)
\]