原式=1/2[(1+1/2+1/3+1/4+……+1/48)+(1/3+1/4+1/5+……+1/49+1/50)-(1+2/3+2/4+2/5+……+1/48+1/49)]
=1/2(1+1/2+1/49+1/50-1-2/49)
=1/2(1/2-1/49+1/50)
=1/2(1/2-1/2450)
=1/4(1-1/1225)
=306/1225
原式=1/2[(1+1/2+1/3+1/4+……+1/48)+(1/3+1/4+1/5+……+1/49+1/50)-(1+2/3+2/4+2/5+……+1/48+1/49)]
=1/2(1+1/2+1/49+1/50-1-2/49)
=1/2(1/2-1/49+1/50)
=1/2(1/2-1/2450)
=1/4(1-1/1225)
=306/1225