1/2[(1/2-1/4)+(1/4-1/6)+...+(1/16-1/18)]x128
=1/2x(1/2-1/18)x128
=(1/2)x(8/18)x128
=2/9x128
=256/9
(1/8+1/24+1/48+1/80+1/120+1/168+1/224+1/288)x128
=(2/8+2/24+2/48+2/80+2/120+2/168+2/224+2/288)×64
=(1/2-1/4+1/4-1/6+1/6-1/8+1/8-1/10+1/10-1/12+1/12-1/14+1/14-1/16+1/16-1/18)×64
=(1/2-1/18)×64
=(9/18-1/18)×64
=8/18×64
=256/9
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