简便计算:1又1/2-5/6+7/12-9/20+11/30-13/42(要过程)

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简便计算:1又1/2-5/6+7/12-9/20+11/30-13/42(要过程)
简便计算:1又1/2-5/6+7/12-9/20+11/30-13/42(要过程)

简便计算:1又1/2-5/6+7/12-9/20+11/30-13/42(要过程)
1又1/2-5/6+7/12-9/20+11/30-13/42
=(1+1/2)-(1/2+1/3)+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)
=1+1/2-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7
=1-1/7
=6/7

=630/420-350/420+245/420-189/420+154/420-130/420
=6/7