1×2/1998+2×3/1998+3×4/1998+4×5/1998+5×6/1998

来源:学生作业帮助网 编辑:作业帮 时间:2024/11/05 02:26:18
1×2/1998+2×3/1998+3×4/1998+4×5/1998+5×6/1998
x)3<<~CKK{O7FO7ALO7ELO7lb~͠r [C}{:@j ҩ Љ6PHH T hY'gTRaZqi6Pe aaonZ$AC-c h@C `k"!Rôig3?_7餞';;yP1

1×2/1998+2×3/1998+3×4/1998+4×5/1998+5×6/1998
1×2/1998+2×3/1998+3×4/1998+4×5/1998+5×6/1998

1×2/1998+2×3/1998+3×4/1998+4×5/1998+5×6/1998
1×2/1998+2×3/1998+3×4/1998+4×5/1998+5×6/1998
=1/1998×(1×2+2×3+3×4+4×5+5×6)
=1/1998×[1*2+(2*3+3*4)+(4*5+5*6)]
=1/1998×(2*1²+2*3²+2*5²)
=1/1998×70
=35/999

35/999

=(1×2+2×3+3×4+4×5+5×6)/1998
=(2+6+12+20+30)/1998
=70/1998

只是算和么,还是1×2/1998+2×3/1998+3×4/1998+4×5/1998+5×6/1998 +...+[n×(n+1)]/1998
求和的话就35/999