a: Số số hạng là (155-8):3+1=50(số)

b: Số thứ 30 là:

8+29*3=8+87=95

(a) Công thức tính số hạng của dãy số cách đều: \(n=\dfrac{a_n-a_1}{d}+1\) với \(a_n\) là số hạng cuối cùng, \(a_1\) là số hạng đầu tiên và \(d\) là khoảng cách giữa các số hạng.

Dễ thấy, dãy \(S\) gồm các số hạng cách đều \(3\) đơn vị, số hạng đầu là \(8\), số hạng cuối là \(155\), vì vậy, số số hạng của dãy \(S:n=\dfrac{155-8}{3}+1=50\) số hạng.

(b) Số hạng thứ \(30\) là: \(8+3.\left(30-1\right)=95\).

(c) Công thức tính tổng dãy số cách đều: \(\dfrac{\left(a_1+a_n\right)\cdot n}{2}\) với \(a_1,a_n,n\) lần lượt là số hạng đầu tiên, số hạng cuối cùng và số số hạng của dãy.

Áp dụng vào bài toán thì \(S=\dfrac{\left(8+155\right)\cdot50}{2}=4075.\)

Tổng S có tất cả : (155 - 8) : 3 + 1 = 50 (số hạng)

Gọi số hạng thứ 30 của S là x (x ∈ N*)

Khi đó, từ số thứ nhất đến số thứ 30 có số số hạng là:

(x - 8) : 3 + 1 = 30

=> (x - 8) : 3 = 29

      x - 8 = 87

      x = 95 (tmđk)

Vậy số hạng thứ 30 là 95

Tổng S bằng : (155 + 8).50:2=4075

có cái nịt's

1)-(-3)³-(2x+1)³=152

     27-(2x+1)³=152

          (2x+1)³=-125

           (2x+1)³=(-5)³

              2x+1=-5

            2x=-4

              x=-2

2)-(x+6)-34=12+3x

   -x-6-34=12+3x

   -x-3x=12+6+34

      -4x=52

         x=-13

152. Is that her brother? – Yes,  _ his_ _  name is Thomas.

153. Why don’t we go to the  _ _beach _ _ _  this Sunday? 

154. ………….. -  I’m tired.

A. How are you feel. Ken?  B. How do you feel, Ken?

C. How can you feel, Ken?  D. How would you feel, Ken?

155. A. father  B. car  C. care  D. park

156. like / in autumn ? / is / the weather / What

............................What is the weather like in autumn.......................................................................................................................

157. like a / would / chocolate.  /I / box of

..................I would like a box of chocolate .................................................................................................................................

158. What’s the weather _ _ like_ _  in spring in Paris?

159. My little son’s classmate is  _on_  the second floor.

160. Hurry up, or we are late ……………….school.

A. for  B. to  C. at  D. in

161. What time will you arrive ……………the station? – 8 a.m.

A. to  B. in  C. at  D. on

162. has an / library. / The / school / excellent

......................................The school has an excellent library.............................................................................................................

163. Janes wants to go out tonight but she has got too _ _ much_ _  work to do.

164. Does your class _ _ have_ _  forty-five students?

165. My school is at………………………

A. 30 Hoang Hoa Tham Road    B. Hoan Kiem District  

C. a village far frrom here  D. Nam Dinh province

166. Selena eats …………………..every morning.

A. a big breakfast  B. a bowls of noodles  C. rice  D. All are correct

167. STA_MP

168.  _ _Will _ _  you go to church with me this Christmas?

169. Dolphins can’t live in  _ _ _ _ _ _ _ _  water, but a lot of the sea is polluted. (nghe)

170. When do you have math? – We have it  _on_  Mondays.

171. His job is designing buildings. He is a(n)………architect…………………..

172. You can’t ………………………..over the wall. It’s too high. (nghe)

173. Thanks for your helping me carry that box? -  _ My_  pleasure.

174. The other  _ _ name_ _  of Thanksgiving  Day is Turkey Day.

175. Mathew won’t  _ go_  fishing with his friends.

176. My father gave up  smoking be_ _cause  _ _ _   of his coughs.

177. It’s four  _ _ o'clock_ _ _ _ . 

178. _No _ one in my class is taller than Anh.

179. Princess Merida has long  _ _ _ _ _  red hair.

180. They run down…………………..(nghe)

181. Hong likes to help her parents  _ _with _ _  the farm work.

182. Can you go to the supermarket to buy some  _ _ _sausag _ _ _es. 

183. LA_RGE

184.Joe has a ………………………..cake on his birthday? (nghe)

185. There’s  _no _  milk left. You should go to the market to buy some.

186. What’s the weather like today? – It’s  _ _ sunny_ _ _ . 

187. BI_RTH

188. There are a lot of ……………………….under the tree. (nghe)

189. Don’t t_ _ hrow_ _  trash in the street. 

190. Their house is  _ _ _ _between _ _ _  a toy store and a bookstore.

152. Is that her brother? – Yes,  _ his_ _  name is Thomas.

153. Why don’t we go to the  _ _beach _ _ _  this Sunday? 

154. ………….. -  I’m tired.

A. How are you feel. Ken?  B. How do you feel, Ken?

C. How can you feel, Ken?  D. How would you feel, Ken?

155. A. father  B. car  C. care  D. park

156. like / in autumn ? / is / the weather / What

............................What is the weather like in autumn.......................................................................................................................

157. like a / would / chocolate.  /I / box of

..................I would like a box of chocolate .................................................................................................................................

158. What’s the weather _ _ like_ _  in spring in Paris?

159. My little son’s classmate is  _on_  the second floor.

160. Hurry up, or we are late ……………….school.

A. for  B. to  C. at  D. in

161. What time will you arrive ……………the station? – 8 a.m.

A. to  B. in  C. at  D. on

162. has an / library. / The / school / excellent

......................................The school has an excellent library.............................................................................................................

163. Janes wants to go out tonight but she has got too _ _ much_ _  work to do.

164. Does your class _ _ have_ _  forty-five students?

165. My school is at………………………

A. 30 Hoang Hoa Tham Road    B. Hoan Kiem District  

C. a village far frrom here  D. Nam Dinh province

166. Selena eats …………………..every morning.

A. a big breakfast  B. a bowls of noodles  C. rice  D. All are correct

167. STA_MP

168.  _ _Will _ _  you go to church with me this Christmas?

169. Dolphins can’t live in  _ _ _ _ _ _ _ _  water, but a lot of the sea is polluted. (nghe)

170. When do you have math? – We have it  _on_  Mondays.

171. His job is designing buildings. He is a(n)………architect…………………..

172. You can’t ………………………..over the wall. It’s too high. (nghe)

173. Thanks for your helping me carry that box? -  _ My_  pleasure.

174. The other  _ _ name_ _  of Thanksgiving  Day is Turkey Day.

175. Mathew won’t  _ go_  fishing with his friends.

176. My father gave up  smoking be_ _cause  _ _ _   of his coughs.

177. It’s four  _ _ o'clock_ _ _ _ . 

178. _No _ one in my class is taller than Anh.

179. Princess Merida has long  _ _ _ _ _  red hair.

180. They run down…………………..(nghe)

181. Hong likes to help her parents  _ _with _ _  the farm work.

182. Can you go to the supermarket to buy some  _ _ _sausag _ _ _es. 

183. LA_RGE

184.Joe has a ………………………..cake on his birthday? (nghe)

185. There’s  _no _  milk left. You should go to the market to buy some.

186. What’s the weather like today? – It’s  _ _ sunny_ _ _ . 

187. BI_RTH

188. There are a lot of ……………………….under the tree. (nghe)

189. Don’t t_ _ hrow_ _  trash in the street. 

190. Their house is  _ _ _ _between _ _ _  a toy store and a bookstore.

#hoang hai yen :

đề bài là j zậy bn

tìm x à

bằng -51 hoặc 150 nha bn

Hình như đề sai!

( - 152 ) - ( 3x+1 ) = (-2) . (-77)

 (- 152 ) - (3x +1 ) = 154

                3x +1   = (-152)- 154

                 3x + 1 = -306

                 3x       = - 306 - 1

                 3x       = - 307

                   x       = - 307 : 3

                   x       = - 307 / 3 ( dấu / là chỉ phân số) 

x = - 307 / 3

a, => x= -9. 2

=> x= -18

b, => x= 12. (-4)

=> x=-48

c, => 152-(3x-1)=54

=> (3x-1)= 152- 54= 98

=> 3x= 98+1= 99

=> x = 99:3

=> x = 33

tick cho mik nha

Ta có:

a) \(x:2=-9\Rightarrow x=\left(-9\right).2=-18\)

b)\(x:\left(-4\right)=12\Rightarrow x=12.\left(-4\right)=-48\)

c)\(x+x+80=-8\Rightarrow2x+80=-8\Rightarrow2x=-8-80=-88\Rightarrow x=\left(-88\right):2=-44\)d)\(152-\left(3x-1\right)=\left(-2\right).\left(-27\right)=54\Rightarrow152-54=3x-1\Rightarrow98=3x-1\Rightarrow3x=99\Rightarrow x=33\)