1/2*4+1/4*6+1/6*8+…﹢早亩1/98*100 =(1/2-1/4+1/4-1/6+1/6-1/8+……颂举+1/98-1/100)陆樱森/2=(1/2-1/100)/2=49/200
1/2*4+1/4*6+1/6*8+…﹢1/98*100=1/2﹙1/2-1/铅桐颂轮烂4+1/4-1/6+1/6-1/8+······+1/98-1/100﹚=1/2﹙1/2-1/槐郑100﹚=1/2×49/100=49/200