cho dd X gồm HCl 0.5M và dung dịch Y gồm Na2CO3 0.2M VÀ NaHCO3 0.4M .

Rót từ từ 100ml dung dịch X vào dung dịch Y thu được a mol CO2

Rót từ từ 100ml dung dịch Y vào dung dịch X thu được b mol khí CO2.

tỉ lệ giữa a và b là

A. 2/3

B.4/5

C.1/2

D.4/3

Mong mọi người giúp em với ạ!

tìm giá trị nhỏ nhất của biểu thức

a) f(x)= \(\left|x+\dfrac{1}{x}\right|\)(x \(\ne\)0)

b) f(x) = \(x^2+2x+\dfrac{1}{x+1}\)(x>-1)

mong mọi người giúp đỡ với ạ!

giải hệ phương trình

\(\left\{{}\begin{matrix}\dfrac{2x}{x+y}+\dfrac{1}{\sqrt{x}-1}=3\\\dfrac{3y}{x+y}+\sqrt{x}=-2\end{matrix}\right.\)

1. the rising level of air pollution has caused concern among ... (environment)

2. many factories still allow ... ( pollute), such as toxic waste, to flow into our rivers.

3. make sure that the use of ... ( pest) is not harmful to farmer's health.

chọn câu có nghĩa tương đương:

1.he came out of the room and didn't say a word.

a) he came out of the room and not to say a word.

b)he came out of the room without saying a word.

c)he came out of the room but not saying a word

d)all are correct.

2. would you mind opening the window, please?

a) would you please to open the window, please?

b) would you opening the window, please?

c) would you mind to open the window,please?

d)would you please open the window?

3. because they made too many mistakes, they failed in the exam.

a) they made so may mistakes that failing in the exam.

b)they made so many mistakes that they failed in the exam.

c)they made so many mistakes for them to fail in the exam.

d) they made too many mistakes that they failed in the exam.

4. you will avoid waiting by booking a table in advance.

a) if you will book a table in advance, you'll avoid waiting.

b)you will avoid waiting unless you book a table in advance.

c) if you don't book a table in advance, you don't avoid waiting.

d) if you book a table in advance, you will avoid waiting.

1. they are living in a (beauty)... decorated house.

2. some plants grow well with a (minimize)... of care.

3. don't be afraid of that dog. it's completely ... (harm)

4. they carried out ... (provide) with us

1. several people made... at the wedding

a) words

b)letters

c)speechs

c)lectures

2. the woman ... the baby in an old blanket.

a) covered

b)put

c)wrapped

d)held