作业帮1/12*13 1/13*14 1/14*15 .1/19*20()1/12*13+1/13*14+1/14*15+.+1/19*20()1/2+1/1/12+1/20+1/30+1/42()详细步骤
来源：学生作业帮助网 编辑：作业帮 时间：2024/12/01 10:10:45
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1/12*13 1/13*14 1/14*15 .1/19*20()1/12*13+1/13*14+1/14*15+.+1/19*20()1/2+1/1/12+1/20+1/30+1/42()详细步骤
1/12*13 1/13*14 1/14*15 .1/19*20()
1/12*13+1/13*14+1/14*15+.+1/19*20()1/2+1/1/12+1/20+1/30+1/42()详细步骤
1/12*13 1/13*14 1/14*15 .1/19*20()1/12*13+1/13*14+1/14*15+.+1/19*20()1/2+1/1/12+1/20+1/30+1/42()详细步骤
1/12*13+1/13*14+1/14*15+.+1/19*20=1/12-1/13+1/13-1/14+...+1/19-1/20=1/12-1/20=1/301/2+1/6+/12+1/20+1/30+1/42=1/(1*2)+1/(2*3)+...+1/(6*7)=1-1/2+1/2-1/3+1/3-1/4+...+1/6-1/7=1-1/7=6/7