gj0427
幼苗
共回答了22个问题采纳率:90.9% 举报
1、
=1000+(1+3+5+……+999)+(1/4+1/4+……+1/4)-(2+4+6+……+1000)-(1/5+1/5+……+1/5)
=1000+(1+3+5+……+999)+(1/4+1/4+……+1/4)-(2+4+6+……+1000)-(1/5+1/5+……+1/5)
=(1000-1000)+(999-998)+(997-996)+……+(3+2)+1+1/4×500-1/5×500
=0+1+1+……+1+125-100
=1×500+125-100
=525
2、
=4+5+6+7+8+9-(17/39)×(9+8+7+6+5+4)
=(1-17/39)×(9+8+7+6+5+4)
=(22/39)×39
=22
3、
=6985×7138-1985×1593-2564×6985-2981×1985
=6985×(7138-2564)-1985×(1593+2981)
=6985×4574-1985×4574
=(6985-1985)×4574
=5000×4574
=5000×2×4574÷2
=10000×2287
=22870000
1年前
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