(1/m^2-3m)+(1/m^2-9m+18)+(1/m^2-15m+54)

问题描述:

(1/m^2-3m)+(1/m^2-9m+18)+(1/m^2-15m+54)
化简:(1/m^2-3m)+(1/m^2-9m+18)+(1/m^2-15m+54)

=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)