làm được có câu b à xin lỗi nhé

b)
2Fe + 3Cl2 -to-> 2FeCl3

2FeCl2 + Cl2 --> 2FeCl3

6FeSO4 + 3Cl2 --> 2Fe2(SO4)3 + 2FeCl3

Fe2O3 + 6HCl --> 2FeCl3 + 3H2O

3FeCl2 + KNO3 + 4HCl -to-> FeCl3 + NO + KCl + 2H2O

3BaCl2 + Fe2)SO4)3 --> 2FeCl3 + 3BaSO4

Fe(OH)3 + 3HCl --> FeCl3 + 3H2O

9Fe(NO3)2 + 12HCl --> 5Fe(NO3)3 + 4FeCl3 + 3NO + 6H2O

4FeCl2 + 4HCl + O2 --> 4FeCl3 + 2H2O

3FeCl2 + 4HNO3 --> Fe(NO3)3 + 2FeCl3 + NO + 2H2

a, vì a > b nên 3a > 3b => 3a + 2 > 3b + 2 (1)

Mà 3a + 2 < 3a + 5 (2)

Từ (1) và (2) suy vô ra : 3a + 5 > 3b+2 (đpcm)

b, vì a > b nên -4a < -4b => 2-4a < 2- 4b

mà 2-4b < 3-4b nên 2-4a < 3-4b

1.My sister and I (stay ) .........STAYED............. at our grandparents when we (meet ) .....HAVE MET.......our great grand aunt for the first time. She (live).....LIVED........... in Australia but for the last month she (be)......WAS....... in Europe. My cousin, in fact (be).....WAS..... norn in Sydney, and he (go).............WENT.... to school there, but now he (live)...IS LIVING....... over here.

2. London (change) ……HAS BEEN CHANGED………… . a lot since we first came to live here.
3. You (finish) ……HAVE YOU FINISHED………… . with the bathroom yet?
4. How many lessons you (miss) ………HAVE YOU MISSED……… . this year?
- Only one, and that (be) ………WAS……… . because I had flu in November.

có gì thì lên học 24h hỏi nha

1+2+3+4+5+6+7+8+9+10=(10+1)x10:2=55

1 + 2 + 3 + 4 + ... + 100 + 101 + 102 

= (1 + 102) + (2 + 101) + ... + (51 + 52)

    Có : [(102 - 1) + 1] : 2 = 51 (cặp số)

= 103 + 103 + 103 + ... + 103 + 103

= 103 x 51 

= 5253

1 + 2 + 3 + 4 + 5 + .... + 100 + 101 + 102 ( có 102 số hạng)

= ( 1 + 102) x 102 : 2

= 103 x 51

= 5253 

nhiều nhỉ lấy ở đâu đấy !!!!!!!!!!!!!!!!!!!!!!!!!