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1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45等于多少要写具体的过程,为什么
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1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45等于多少 要写具体的过程,为什么
▼优质解答
答案和解析
1/3+1/6+1/10+1/15+1/21+1/28+1/36+1/45
=(1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90)*2
=(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10)*2
=(1/2-1/10)*2=1-1/5=4/5
=(1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90)*2
=(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10)*2
=(1/2-1/10)*2=1-1/5=4/5
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