Step 1: Understanding the Concept
The point dividing \((1,1)\) and \((2,4)\) internally in the ratio \(3:2\) is \(\left(\dfrac{3\cdot2+2\cdot1}{5},\dfrac{3\cdot4+2\cdot1}{5}\right)\).
Step 2: Point
This is \(\left(\dfrac{8}{5},\dfrac{14}{5}\right)\).
Step 3: Find k
\(k=2x+y=\dfrac{16}{5}+\dfrac{14}{5}=6\).
Step 4: Ratio
\((k+1):(k-1)=7:5=\dfrac{7}{5}\), option (B).
Final Answer:
The ratio \((k+1):(k-1)\) equals \(\dfrac{7}{5}\).
\[ \boxed{\text{(B) }\dfrac{7}{5}} \]