=1/m(m-3)+1/(m-3)(m-6)+1/(m-6)(m-9)
=1/3[3/m(m-3)+3/(m-3)(m-6)+3/(m-6)(m-9)]
=1/3[1/(m-3)-1/m+1/(m-6)-1/(m-3)+1/(m-9)-1/(m-6)]
=1/3[1/(m-9)-1/m]
=3/(m²-9m)
=1/m(m-3)+1/(m-3)(m-6)+1/(m-6)(m-9)
=1/3[3/m(m-3)+3/(m-3)(m-6)+3/(m-6)(m-9)]
=1/3[1/(m-3)-1/m+1/(m-6)-1/(m-3)+1/(m-9)-1/(m-6)]
=1/3[1/(m-9)-1/m]
=3/(m²-9m)