1/X(X+3)+1/(X+3)(X+6)+1/(X+6)(X+9)=3/2X+18 规律是1/X(X+3)=1/X-1/(X+3)

问题描述:

1/X(X+3)+1/(X+3)(X+6)+1/(X+6)(X+9)=3/2X+18 规律是1/X(X+3)=1/X-1/(X+3)

1/X(X+3)=1/X-1/(X+3)错误.
正确:1/X(X+3)=1/3[1/X-1/(X+3)]