As y−axis is tangent to the circle therefore the centre of the circle would be (x,2) and distance of centre from (0,2) and (−2,4) should be equal.
∴ h2+02=(h+2)2+22
⇒h2=h2+4h+4+4
⇒h=−2
Hence, centre is (−2,2).
∴ 2x−3y+10=0 is the diameter, as centre lies on it.