2/51+4/51+6/51+...50/51-1/51-3/51-...-49/51 2/51+4/51+6/51+...50/51-1/51-3/51-...-49/51 请高手指教,

2/51+4/51+6/51+...50/51-1/51-3/51-...-49/51 2/51+4/51+6/51+...50/51-1/51-3/51-...-49/51 请高手指教,
2/51+4/51+6/51+...50/51-1/51-3/51-...-49/51
2/51+4/51+6/51+...50/51-1/51-3/51-...-49/51 请高手指教,

2/51+4/51+6/51+...50/51-1/51-3/51-...-49/51 2/51+4/51+6/51+...50/51-1/51-3/51-...-49/51 请高手指教,
2/51+4/51+6/51+...50/51-1/51-3/51-...-49/51=（2/51-1/51)+(4/51-3/51)+……+(50/51-49/51)=25*1/51=25/51

2、4、6....50可以记作2n （n=1、2、3....25）
1、3、5....49可以记作2n-1(n=1、2、3....25)
份母相同：
原式=n*{[2n-(2n-1)]/51}=n*[(2n-2n+1)/51]=n*1/51=25/51

2/51+4/51+6/51+...50/51-1/51-3/51-...-49/51
=2/51-1/51+4/51-3/51+……+50/51-49/51
=1/51*25
=25/51