H.M. = 4, A.M. = (\dfrac{9}{2})

[ \dfrac{x+y}{2}=\dfrac{9}{2}\implies x+y=9 ] [ \dfrac{2xy}{x+y}=4\implies\dfrac{2xy}{9}=4\implies xy=18 ]

[ t^2-9t+18=0\implies(t-6)(t-3)=0 ]

Answer: 3 and 6