1/2+1/8+1/24+.+1/9800

原式=1/2+(1/8+1/24+···+1/9800)=1/2+1/2*(1/2-1/4+1/4-1/6+···+1/98-1/100) =1/2+1/2*49/100 =1/2+49/50 =25/50+49/50 =74/50=3...1/2+1/2*(1/2-1/4+1/4-1/6+···+1/98-1/100)什么意思1/8+1/24+···+1/9800=1/2*(1/2-1/4+1/4-1/6+···+1/98-1/100)这是分数的裂项1/2再加上