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a: Ta có: ΔABC cân tại A

mà AM là đường trung tuyến

nên AM là đường cao

b: Ta có: ΔABC cân tại A

mà AM là đường cao

nên AM là đường phân giác

c: Ta có: ΔABC đều

nên $\widehat{ABM}=\widehat{ACM}={60}^0$

c

... ;-;

b

tk

VI- Give the correct forms of the words in parentheses

1- English is an ...........interesting................ and important subject. (interest)

2- My country is rich in .............natural................ resources. (nature)

3- My father can read ..........well........... without glasses. (good)

4- We had an interesting ............discussion............... about football. (discuss)

5- During his ...............childhood........... the family lived in Cornwall. (child)

6- It's ...........dangerous............. to cross the avenue. (danger)

7- Could you give me some...........information..............? (inform) 8- Are you a ...........tourist........... or are you living here ? (tour)

9- The shoes were nice, but they were .......comfortable ........................ (comfort)

10- Surface mail is much ..........cheaper..................... than airmail. (cheap)

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c

Gọi công thức của oxit là A₂O₃

Ta có A₂O₃ + 6HCl → 2ACl₃ + 3H₂O

Từ pthh ta có n_A2O3 = 1/6 nHCl = 1/6 . 0,3 = 0,05 mol

=> M_A2O3 = m_A2O3 : n_A2O3 = 5,1 : 0,05 = 102

M_A2O3 = 2 . MA + 3 . 16 = 2MA + 48 = 102

=> MA = 27 => A là nhôm

=>Al₂O₃+3H₂SO₄->Al₂(SO₄)₃+3H₂O

    0,05-----0,15 mol

=>m dd H2SO4=58,8g