choA=5+52+53+54+...+58
Chung to A la bội của 30
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AH
Akai Haruma
Giáo viên
13 tháng 12 2021
Lời giải:
$A=(5-5^2)-(5^3+5^4)-(5^5+5^6)$
$=5(1-5)-5^4(1+5)-5^5(1+5)$
$=-20-5^4.6-5^5.6=-20-30.5^3-30.5^4$
$=-20-30(5^3+5^4)$ không chia hết cho $30$ cho $20$ không chia hết cho $30$
Do đó $A$ không thể là bội của $30$
CC
1
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
18 tháng 8 2023
A = 5 + 52 + 53 +...+ 58
A = (5 + 52) +( 53 + 54) +...+ ( 57 + 58)
A = 30 + 52.(5 + 52) +...+ 56.(5 + 52)
A = 30.( 1 + 52 +...+ 56) (đpcm)
CM
9 tháng 12 2019
Ta có: A = 5 + 5 2 + 5 3 + 5 4 + 5 5 + 5 6 + 5 7 + 5 8
= 5 + 5 2 + 5 2 5 + 5 2 + 5 4 5 + 5 2 + 5 6 5 + 5 2
= 30 + 5 2 . 30 + 5 4 . 30 + 5 6 . 30
= 30 . ( 1 + 5 2 + 5 4 + 5 6 ) ⋮ 30
Vậy A là bội của 30
CM
27 tháng 10 2017
a, A = 5 + 5 2 + 5 3 + . . . + 5 8
= 5(1+5)+ 5 2 (1+5)+ 5 3 (1+5)+...+ 5 7 (1+5)
= 30+5.30+ 5 2 .30+...+ 5 6 .30
= 30.(1+5+ 5 2 +..+ 5 6 )
Vậy A là bội của 30
b, B = 3 + 3 3 + 3 5 + 3 7 + . . . + 3 29
= 3 1 + 3 2 + 3 4 + 3 7 1 + 3 2 + 3 4 +...+ 3 27 1 + 3 2 + 3 4
= 273+273. 3 6 +...+ 3 26 .273
= 273.(1+ 3 6 +...+ 3 26 )
Vậy B là bội của 273
NT
Nguyễn Thị Thương Hoài
Giáo viên
VIP
7 tháng 11 2023
Đề bài thiếu yêu cầu cụ thể em nhé. em cập nhật lại câu hỏi để được sự hỗ trợ tốt nhất cho tài khoản olm vip
TH
0
22 tháng 5 2022
Câu 52: Don’t eat chocolate and candy everyday. ( sô – cô – la )
Câu 53: … does it cost to send this present to Ho Chi Minh ?
A. How many B. How far C. How often D. How much
Câu 54: When I was a child, my father often … stories about Uncle Ho.
A. spoke B. told C. tell D. talked
Câu 55: so we don’t / waste water. / We collect / for cleaning/ rain water
=> We collect rain water for cleaning so we don't waste water.
Câu 56: Where are / you going / to stay during / your vactions / in Hoi An?
=> Where are you going to stay during your vacation in Hoi An?
Câu 57: I would like some rice. I’m hungry .
Câu 58: There were too many people at Binh’s party yesterday.
Câu 59: I usually go to bed at 10:30 but today I … computer games.
A. am surfing B. surf C. play D. am playing
Câu 60: If you have a bad cold, you should … some panadol capsules.
A. make B. eat C. chew D. take
Câu 61: She has / a pain / on her arm. / Cindy fell / off her bike
=> Cindy fell off her bike. She has a pain on her arm..
Câu 62: the office / after finishing / all his work. / My father / leaves
=> My father leaves the office after finishing all his work.
Câu 63: Jack has got a horse, three dogs and two cats. ( con ngựa )
Câu 64: Do you live in a flat? ( căn hộ )
Câu 65: Would you like … to the movies with us to night?
A. going B. goes C. to go D. to going
Câu 66: Joana lives … 60 Rosa Aenue … Oxford in England.
A. at / in B. on / in C. at / at D. at / on
Câu 67: there a / Excuse me, / near here? / is / restaurant
=> Excuse me, is there a restaurant near here?
Câu 68: the capital? / and move to / Are you / going to / sell your house
=> Are you going to sell your house and move to the capital?
Câu 69: Western people often go to the church at Christmas.
Câu 70: It’s going to rain so you should take an umbrella.
Câu 71: Who was your favourite … in the play ?
A. book B. author C. character D. audience
Câu 72: I like learning English best. It is my … favourite subjects -> subject.
A. a B. the C. 0 D. an
Câu 73: before / having lunch? / didn’t you/ Why / wash your hands
=> Why didn't you wash your hands before having lunch?
Câu 74: old / is / drive a car. / enough to / My brother
=> My brother is old enough to drive a car.
Câu 75: Did you borrow my umbrella yesterday ? – No, I didn’t.
Câu 76: Have you got a garden. ( khu vườn )
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A. science B. scientific C. scientist D. scientists
Câu 78: My penpal is French. What’s your new penpal’s …?
A. city B. from C. nationality D. country
Câu 79: good programs / They aren’t / at the moment. / any / showing
=> They aren't showing any good preograms at the moment.
Câu 80: worry. / but don’t / how / you feel, / I understand
=> I understand how you feel, but don't worry.
Câu 81: Tommy’s mother has two sons. One son is called John. Another son is Jack.
Câu 82: There is a pencil on the table, but it doesn’t belong to me.
Câu 83: If you want to have a healthy body, you should play …
A. computer games B. exercises C. songs D. Sports
Câu 84: Choose the word that has the underlined part pronounced differently from the other.
A. bus B. but C. picture D. up
Câu 85: gave her / bicycle for / a white / her birthday. / Ngoc’s parents
=> Ngoc's parents gave her a white bicycle for her birthday.
Câu 86: Do you want / to see / what life / is like under / the ocean ?
=> Do you want to see what life is like under the ocean?
Câu 87: Does she comb her hair every morning ?
Câu 88: Viets lives with his aunt and uncle at 83 Nguyen Trai Street.
Câu 89: My brother and I … a kite last Sunday.
A. flied B. flew C. were flywing D. did fly
Câu 90: Lien’s brother is an architect but he … at the moment.
A. dosen’t work B. didn’t work C. not work D. isn’t work => isn't working
Câu 91: to your health. / Don’t play video / games to much / It can be / harmful
=> Don't play video games too much. It can be harmful to your health.
Câu 92: Jack ate bread for / and a sandwich / breakfast at half past six/ for lunch at / a quarter to twelve.
=> Jack ate bread for breakfast at half past six and a sandwich for lunch at a quarter to twelve.
Câu 93: They don’t eat anything because they are afraid of being late for school.
Câu 94: I am too tired to do all my homework today.
Câu 95: I’m going to the amusement center. I’m going to play video games…
A. here B. that C. there D. this
Câu 96: We see lots of flowers in … ( mùa xuân )
A. summer B. spring C. September D. Christmas
Câu 97: at school / activities/ next Monday. / part in different / We will take
=> We will take part in different activities at school next Monday.
Câu 98: take you to / will it / by bus? / get there / How long
=> How long will it take you to get there by bus?
Câu 99: I sometimes go to the cinema in June.( rạp chiếu phim)
Câu 100: Monkeys can climb and jump.
22 tháng 5 2022
59 D ắ e
cấu trúc thể hiện sự khác thường so với mọi người ngta dùng hiện tại tiếp diễn
77 A science subjects hay sao í
89 B fly - flew - flown
A=5+52+53+.....+58
A có 8 số hạng,ghép 2 số thành 1 cặp lần lượt từ trái sang phải,ta có:
A=(5+52)+(53+54)+...+(57+58)
A=30+52.30+...+56.30
A=30.(52+54+...+56) chia hết cho 30
Vậy A là bội của 30
Chúc em học tốt^^