viết đoạn văn 5 đến 7 câu giới thiệu về lớp học . trong đó có dùng các danh từ chỉ đơn vị tự nhiên và đơn vị quy ước.

các bạn giúp mk với mk cảm ơn trước nhé!

chia động từ trong ngoặc

1.have You (make) made up your mind yet ?

2.Tom (participate) has participated in Green Summer programme before ?

3.So far, he (do) has done the volunteer work.

4.The children (not finish) haven't finished painting yet.

5.We (work) have worked together for several months.

6.I (invite) invited them to my party yesterday,but they (not come) didn't come.

7.Jane (leave) has just left a minute ago.

8.When did you (start) start your volunteer work ?

Ta có: \(B=\frac{2}{1.4}+\frac{2}{4.7}+...+\frac{2}{22.25}\)

\(\Rightarrow\frac{3}{2}B=\frac{1}{1.4}+\frac{1}{4.7}+...+\frac{1}{22.25}\)

\(\Rightarrow\frac{3}{2}B=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+...+\frac{1}{22}-\frac{1}{25}\)

\(\Rightarrow\frac{3}{2}B=1-\frac{1}{25}=\frac{24}{25}\)

\(\Rightarrow B=\frac{24}{25}:\frac{3}{2}=\frac{16}{25}\)

bn ui mk chưa hỉu lắm, bn giải thk kĩ hơn chút mk cho

a) Ta có: \(A=\frac{3}{10.12}+\frac{3}{12.14}+....+\frac{3}{998.1000}.\)

 \(\Rightarrow\frac{2}{3}A=\frac{1}{10.12}+\frac{1}{12.14}+...+\frac{1}{998.1000}\)

 \(\Rightarrow\frac{2}{3}A=\frac{1}{10}-\frac{1}{12}+\frac{1}{12}-\frac{1}{14}+...+\frac{1}{998}-\frac{1}{1000}\)

 \(\Rightarrow\frac{2}{3}A=\frac{1}{10}-\frac{1}{1000}=\frac{99}{1000}\)

 \(\Rightarrow A=\frac{99}{1000}:\frac{2}{3}=\frac{297}{2000}\)

Có 56 số

dòng trên cùng bạn bỏ đi nhé mk viết nhầm ~~

tom has trouble with his group he doesn't get used to work with others

=> tom has trouble with his group he doesn't get used to working with others

12+(5+x)=20

(5+x)     = 20-12

5+x       =8

x           =8-5

x           = 3