1⼀10*11+1⼀11*12+1⼀12*13+.+1⼀19*20如何简便计算

2024-12-17 19:12:58
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回答1:

由于1/10*11=1/10-1/111/11*12=1/11-1/121/12*13=1/12-1/13..所以原式==(1/10-1/11)+(1/11-1/12)+(1/12-1/13)+.+(1/19-1/20) =1/10-1/11+1/11-1/12+1/12-1/13+.+1/19-1/20 =1/10-1/20 =1/20