1/2×4+1/4×6+1/6×8+.+1/2006×2008 等于多少

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1/2×4+1/4×6+1/6×8+.+1/2006×2008 等于多少
1/2×4+1/4×6+1/6×8+.+1/2006×2008 等于多少

1/2×4+1/4×6+1/6×8+.+1/2006×2008 等于多少
1/2×4+1/4×6+1/6×8+.+1/2006×2008
=1/4(1-1/2+1/2-1/3+1/3-1/4+------+1/1003-1/1004)
=1/4(1-1/1004)
=1003/4016

原式=1/2(1/2 -1/4 +1/4 -1/6+……+1/2006 -1/2008)
=1/2(1/2-1/2008)
=1/2*(1003/2008)
=1003/4016

1/2×4+1/4×6+1/6×8+.......+1/2006×2008
=1/2*[(1/2-1/4+1/4-1/6+......+1/2006-1/2008)]
=1/2(1/2-1/2008)
=1/2*1003/2008
=1003/4016

原式=1/2(1/2-1/4+1/6-1/8........+1/2006-1/2008)
=1/2(1/2-1/2008)
=1003/4016

1/(2*4)=1/2*(4-2)/(4*2)=1/2*(1/2-1/4)
同理1/(4*6)=1/2(1/4-1/6)……1/(2006*2008)=1/2(1/2006-1/2008)
加起来就是1/2(1/2-1/2008)=1003/4016

=1/2(1/2-1/4+1/4-1/6......+1/2006-1/2008)
=1/2(1/2-1/2008)
=1003/4016

都提出个1/4
原式=1/4(1/1*2 + 1/2*3 + ... + 1/1003*1004)
=1/4(1-1/2 + 1/2-1/3 + 1/3-1/4 + .... + 1/1003-1/1004 )
=1/4(1-1/1004)
=1/4(1003/1004)
=1003/4016