Recovering a reciprocal law from a straight line

For \(x>0\), the graph of \(xy\) against \(x\) is a straight line with gradient \(2\) passing through \((1,5)\).

1. Express \(y\) in terms of \(x\).[2]
2. Find the value of \(x\) for which \(y=2.5\).[1]
3. The straight line meets the vertical axis at \((0,3)\). Explain why this does not correspond to a point on the curve \(y\) against \(x\), and describe how \(y\) behaves as \(x\) becomes large.[3]