Ta có:
`1/a+1/b+1/c=2`
`⇔(1/a+1/b+1/c)^2=2^2`
`⇔1/a^2+1/b^2+1/c^2+2/(ab)+2/(bc)+2/(ca)=4`
`⇔1/a^2+1/b^2+1/c^2+2(1/(ab)+1/(bc)+1/(ca))=4`
`⇔1/a^2+1/b^2+1/c^2+2(c/(abc)+a/(abc)+b/(abc))=4`
`⇔1/a^2+1/b^2+1/c^2+2.(a+b+c)/(abc)=4`
Mà `a+b+c=abc`
`\to 1/a^2+1/b^2+1/c^2+2.(abc)/(abc)=4`
`⇔1/a^2+1/b^2+1/c^2+2=4`
`⇔1/a^2+1/b^2+1/c^2=4-2`
`⇔1/a^2+1/b^2+1/c^2=2`
Vậy `1/a^2+1/b^2+1/c^2=2(đpcm)`
Đáp án + Giải thích các bước giải:
`1/a^2+1/b^2+1/c^2=2`
`=>1/a^2+1/b^2+1/c^2+2/(ab)+2/(bc)+2/(ca)=4`
`=>1/a^2+1/b^2+1/c^2+2(1/(ab)+1/(bc)+1/(ca))=4`
`=>1/a^2+1/b^2+1/c^2+2((a+b+c)/(abc))=4`
`=>1/a^2+1/b^2+1/c^2+2((abc)/(abc))=4`
`=>1/a^2+1/b^2+1/c^2+2.1=4`
`=>1/a^2+1/b^2+1/c^2=2`
Vậy `1/a+1/b+1/c=2` và `a+b+c=abc` thì `1/a^2+1/b^2+1/c^2=2`
70. I / ruler / a back / and white / have ; ............................................. 71. is on / my / the third / floor . / classroom ; ............................................ 72 . he _ _ my brother . 73 . don't ma _ _ noise in class . 74. how many desks ......... in your classroom ? a. is there b . are there c . are those d . are there 75 . is .......... a library at your school ? a. thse b. this c. there d. that 76. two dogs . / a cat / and / my brother / has ; ...................................................... 77. your bedroom ? / books / in / any / Are there ; .................................................. 78. her family n _ _ _ is green . 79 . h _ _ is your mother ? - she 's fine 80. w ___ t is this ? - this is a red marker. 81. ..................... many desks are there in your classroom ? a. how b . what c. who d . which 82. how old is your sister ? ............. is fifteen years old 83. hot / summer ? / Is / it / in ; ....................................................... 84 . likes / baby / my / sweets / brother; ............................................ 85. cr _ _ on. 86. my baby sister í beautifui . ............................ is five years old a. he b. she c. they d. it 87. play football / i / often / with/ my brother ;......................................... 88. she / like / dolls / to play / doesn' t ; ................................................ 89. h _ _ name is peter brown . 90 . the book s are _ _ the table . 91. goodbye , see ............... later 92. put on your coat ...... you ' ll get cold . a. but b. or c. and d. so 93. how many / does / have ? / apples / your sister ; ............................................. 94. now . / the computer / in / we are / room ; ...................................................... 95. be qu _ _ _ t plaease . 96 .the woman __ teacher . alice. 97 . which are your favourite toys , dolls ........ robots ? a. and b. for c. or d . at 98. what do you at break time ? play chess a. does b. is c. are d. do 99 . peter / you / see / tomrrow ; .......................................................................
tính rút gọn cho mik câu này 40 điểm
:𝘃 𝗚𝗶𝘃𝗲 𝘁𝗵𝗲 𝗰𝗼𝗿𝗿𝗲𝗰𝘁 𝗳𝗼𝗿𝗺 𝗼𝗳 𝘁𝗵𝗲 𝘄𝗼𝗿𝗱 𝗶𝗻 𝗯𝗿𝗮𝗰𝗸𝗲𝘁𝘀. 1. It took me 2 hours _______ (buy) the clothes and shoes. 2. Do you have any money ________ (pay) for the hat? 3. Would you like ________ (visit) my grandparents in Paris? 4. Don’t waste her time ___________(complain) about her salary 5. That questions need ___________ (reply). 6. Viet is used to ________ (cry) when he faces his difficulties. 7. It’s time they stopped ______ (work) here. 8. Will she remember _______ (collect) his suit from the dry – cleaners or shall do it 9. Jim forgot ________ (send) this message last night. 10. Hung stopped ______ (eat) meat yesterday. (trl đúng & ko chép mạng thì đc chọn "câu trl hay nhất" :v)
qua hình tượng nhân vật Thánh gióng em hãy viết một đoạn văn để nêu cảm nhận của em về vẻ đẹp của nhân vật
giúp mình nhé x ²+y ²+z ²-xy-yz-zx ≥1 với x,y,z ≥0 và x ≥y;x ≥z;x ≥1 điểm rơi x=1 ;y=z=0
Ai giúp mình với III. Choose the correct option A,B,C or D to complete the sentences. 6. A person who . . . . . the bagpipes is called a piper. A. playsB. performsC. entertainsD. does 7. Don’t drink that water. It’s . . . . . A. damagedB. dumpedC. contaminatedD. pollution 8. The team’s success was largely . . . . . to her efforts. A. becauseB. dueC. sinceD. as 9. We don’t have many carnivals in Vietnam; . . . . ., we have many traditional festivals. A. neverthelessB. whileC. althoughD. because 10. When I came, the whole family . . . . . dinner around a big dining table. A. is havingB. was having C. hadD. have 11. While she was dancing, the princess . . . . . a witch. A. was seeing B. saw C. seeD. is seeing 12. The government is sending . . . . . to the flood victims. A. touchB. aidC. accommodation D. provision 13. I often drink coffee, but today I . . . . . tea. A. am drinkingB. drinkC. drankD. drinks 14. By the time we got to the cinema, the film . . . . . A. startedB. had startedC. startingD. starts 15. All our English teachers are . . . . . speakers. A. nativeB. originalC. foreignD. orginally 16. If you were the president, what . . . . . you do to help the environment ? A. will B. wouldC. doD. are 17. When she comes later today, he . . . . . the dinner. A. cooksB. is cookingC. will be working D. has cooked 18. If the teacher were here now, we’d ask him the difference . . . . “science” and “technology”. A. amongB. of C. betweenD. for 19. Our teacher says that new technology . . . . . many worker jobless in the future. A. makesB. is makingC. will makeD. has made 20. . . . . . ethnic minority people in the village are very friendly. A. aB. theC. anD. θ 21. The song “The road to glory days” . . . . . by Tran Lap is a very popular song. A. composeB. composedC. composingD. to compose 22. Alexander Graham Bell was a great . . . . ., who invented the telephone. A. developerB. conservationistC. scientistD. explorer V. Rewrite the sentences so that it stays the same meaning. 28. You should water these flowers regularly. These flowers should …………………………………………… 29. “ I have decided to become an astronomer”, he said. He said that ………………………………………………………. 30. Let's go abroad for our holiday this year. Why ……………………………………………………………… 31. During dinner, the phone rang. While I …………………………………………………………… VI. Rearrange the words to make meaningful sentences. 32. New York/ the/ but/ is/ city/ the USA/ the/ in/ not/ biggest/capital./ 33. English/ an/language/ Malaysia/ India/ many/ is/ official/ in/ and/ other countries./ 34. English speakers/ increasing/ the/ of/ number/ world/ is/ the/ in/ fast./ 35. whereas/ capital/ of/ the/ London/ of/ Edinburgh/ capital/ England/ the/ is/ is/ Scotland./
Write the word in the correct order
Vẽ ảnh sau ạ UwU, không cần quá giống đou nhoa, hóng các idolll
Lm hộ mk vs 10h phải nộp :'(( ko dài lắm đâu
1/3+1/3^2+1/3^3+1/3^4+...+1/3^99+1/3^100
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