求大神用简便运算算出来这些题,谢谢~1+1/4+9/20+11/30-13/42+15/5622又1/20x1/211/7x57x57又1/61+3又1/6+5又1/12+7又1/20+9又1/30+11又1/42+13又1/56

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求大神用简便运算算出来这些题,谢谢~1+1/4+9/20+11/30-13/42+15/5622又1/20x1/211/7x57x57又1/61+3又1/6+5又1/12+7又1/20+9又1/30+11又1/42+13又1/56
求大神用简便运算算出来这些题,谢谢~
1+1/4+9/20+11/30-13/42+15/56
22又1/20x1/21
1/7x57x57又1/6
1+3又1/6+5又1/12+7又1/20+9又1/30+11又1/42+13又1/56

求大神用简便运算算出来这些题,谢谢~1+1/4+9/20+11/30-13/42+15/5622又1/20x1/211/7x57x57又1/61+3又1/6+5又1/12+7又1/20+9又1/30+11又1/42+13又1/56
1+1/4-9/20+11/30-13/42+15/56
=1+1/4-1/4-1/5+1/5+1/6-1/6-1/7+1/7+1/8
=1+1/8
=1又1/8
22又1/20x1/21
=(21+21/20)×1/21
=21×1/21+21/20×1/21
=1+1/20
=1又1/20
1/7x57又1/6
=1/7×(56+7/6)
=(1/7×56+1/7×7/6)
=8+1/6
=8又1/6
1+3又1/6+5又1/12+7又1/20+9又1/30+11又1/42+13又1/56
=(1+3+5+7+9+11+13)+(1/6+1/12+1/20+1/30+1/42+1/56)
=7×7+(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8)
=49+1/2-1/8
=49又3/8