Biểu diễn nghiệm pt cos x=0 trên đường tròn lượng giác

Tìm m để pt có nghiệm 2sin (x+π/3)-2m+1=0

Xác định thành phần % theo khối lượng của 50g đá vôi khi phân hủy Canxicacbonat thành 22.4g canxioxit và 17.6g Cacbonđioxit 

Tính nồng độ mol/l của dung dịch $H_{2}S{O}_4$ và NaOH biết rằng:

-20ml dung dịch $H_{2}S{O}_4$ được trung hòa hết bởi 20ml dung dịch NaOH và 8ml dung dịch KOH 1M

-50ml dung dịch NaOH được trung hòa hết bởi 20ml dung dịch $H_{2}S{O}_4$ và 10ml dung dịch HCl 2,8M

Her thoughtless comments made him very angry.OPPOSITE

A.   honest      B.   kind          C.   pleasant                D. thoughtful

She is a very generous old woman. She has given most of her wealth to a charity organization.OPPOSITE

We are now a 24/7 society where shops and services must be available all hours.OPPOSITE

A.  an active society              B. an inactive society

C.  a physical society             D. a working society

His replies were inconsistent with his previous testimony.

OPPOSITE

A.   contradicted        B.    compatible           C.   enhanced              D. incorporated

Solar energy is not only plentiful but also infinite.OPPOSITE

Mountain people of adjoining nations have great deal in common because terrain and climate mould their lives similarly.CLOSEST

The music is what makes the movie so memorable.CLOSEST

The warranty guaranteed that all defective parts would be replaced without charge.CLOSEST

In remote communities, it's important to replenish stocks before the winter sets in.OPPOSITE

A.   empty       B.    refill         C.   repeat       D. remake

There has been no discernible improvement in the noise levels since lorries were banned.OPPOSITE

Roget's Thesaurus, a collection of English words and phrases, was originally arranged by the ideas they express rather than by alphabetical order.CLOSEST

A.   restricted              B.  as well as              C.   unless                   D. instead of

The teacher gave some suggestions on what could come out for the examination.CLOSEST

With the dawn of space exploration, the notion that atmospheric conditions on Earth may be unique in the solar system was strengthened.CLOSEST

A.   expansion             B.   beginning             C.   continuation         D. outcome

A lack of qualifications can be a major obstacle to finding a job.CLOSEST

"What I've got to say to you now is strictly off the record and most certainly not for publication," said the government official to the reporter.CLOSEST

I think the medicine is beginning to wear off.CLOSEST

A.  stop being effective         B. take effect

C. be put in  a bottle              D. be swallowed

My cousin tends to look on the bright side in any circumstance.OPPOSITE

It was apparent from her face that she was really upset.OPPOSITE

A.   obvious                B.   indistinct              C.   transparent           D. evident

Many scientists agree that global warming poses great threats to all species on Earth.CLOSEST

A.   risks          B.   annoyances           C.   fears         D. irritations

E-cash cards are the main means of all transactions in a cashless society.                      CLOSEST

The works of such men as the English philosophers John Locke and Thomas Hobbes helped pave the way for academic freedom in the modern sense.CLOSEST

In some countries, the disease burden could be prevented through environmental improvements.OPPOSITE

A.  something to stiffer          B. something enjoyable

air conditioner Mary has just bought is very hard to use.CLOSEST

Have you ever read about a famous general in Chinese history who was very incredulous?OPPOSITE

A.    unimaginable       B.   excellent               C.   incredible             D. skeptical

The law applies to everyone irrespective of race, creed, or colour.OPPOSITE

Snow forced many drivers to abandon their vehicles.CLOSEST

The boy was brought up with a family in the countryside.CLOSEST

A.   reared       B.   bred          C.   raised        D. grown

There was nothing they could do but leave the car at the roadside where it had broken down.CLOSEST