1/6+/12+1/20+1/30.+1/90

蝴蝶绰约2022-10-04 11:39:543条回答

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xjrsusy 共回答了17个问题 | 采纳率94.1%: 1/6+/12+1/20+1/30.+1/90
=(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+...+(1/9-1/10)
=1/2-1/10
=2/5; 1年前

evah201983 共回答了590个问题 | 采纳率: 1/2*3+1/3*4+1/4*5+1/5*6+....+1/9*10
=1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+....+1/9-1/10
=1/2-1/10
=2/5; 1年前

刘含章共回答了173个问题 | 采纳率: =1/(2x3) + 1/(3x4) +1/(4x5) + 1/(5x6) +.....+1/(9x10)
=1/2 -1/3+1/3-1/4+1/4-1/5+1/5-1/6+.....-1/9+1/9-1/10
=1/2-1/10
=2/5; 1年前

1+2+4+8+10+12+14+16+18+20+22+24+28+30.+50 捉乌龟的1年前1: 心间小雨共回答了17个问题 | 采纳率88.2%

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30.– Why are you so late?– ( ). 30.– Why are you so late?– ( ). A.It's a shame B.I came across an old friend C.Never mind D.That's all right 31.– I have an appointment with Dr.Johnson.– ( ). A.The appointment is put off B.You look sick and weak C.Please wait for a minute.He is busy now D.Tell me your ID number 32.– May I help you,madam?– ( ). A.Sorry,I have no idea B.Yes,I know what to buy C.You'd better give me a hand D.Yes,I'd like 2 kilos of oranges 33.Once you're into basketball,you'll find( )great fun to play as a way to relax. A.it B.that C.this D.what 34.Last week I bought a flat( )biggest room faced south. A.that B.whose C.which D.where 35.They handed in their paper( ). A.in line B.by turn C.at turn D.in turn 36.– Will you have some dessert,Judy?– ( ). A.No,thank you.I'm on a diet B.Yes,I've had enough C.You are so good at making it D.Oh,I don't mind 37.– Hey,Barbara.You look so pale.– ( ). A.I'm just getting over the flu B.It doesn't matter C.You didn't sleep well last night D.I'm sorry to hear that 38.Let's go to the cinema,( A.will you shan't we B.shan't we C.don't we D.shall we 39.– What subjects are you studying?– ( ). A.Yes,I'm studying history B.I'm studying now C.I'm studying philosophy D.I'm doing my homework 40.I tried( ),but the line was engaged. A.phone B.phoned C.phoning D.to phone 寒寒风风1年前1: 永远的AMI 共回答了18个问题 | 采纳率94.4%

30.B31.C32.D33A34.B35D36.A37.A38.D39.C40.D

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