cho a,b,c,x,y,z > 0 chứng minh rằng : \(\dfrac{x^2}{a}+\dfrac{y^2}{b}+\dfrac{z^2}{c}\ge\dfrac{\left(x+y+z\right)^2}{a+b+c}\)

Read the passage and choose the correct answers.
The National Health Service in Britain has grown into (1)....... big an organisation that it now employs more people (2)........ other in the country. (3)....... efficient an organisation like this may be, it is bound to (4)....... sonner or later but (5)........ the public can do when they occur. The Patients' Asociation gives (6)....... when they think they they have not been properly looked after. At present the Associantion is fighting against the Governmeent's idea (7)........ general health centres for individual doctors. It says it does not want to tell the Health Service (8)....... do but adds that it (9)......... spend more money on improving the standard ò doctors, (10)........ would be cheaper than building health centres.
1. A. a such                 B. such a                   C. so                        D. a so
2. A. than any              B. than some             C. that any               D. that some 
3. A. For                       B. It doesn't mind      C. Whatever            D. However
4. A. make faults          B. do faults                C. make mistakes   D. it is a little
5. A. there is few          B. there is little          C. it is few               D. it is a little
6. A. to people advice  B. people advices      C. people advice    D. to people advices
7. A. of substiuting       B. to substitute           C. of replacing       D. to replace
8. A. that it must           B. that it is to              C. what is to          D. what to
9. A. would have to      B. needs                     C. should              D. ought
10. A. which                 B. what                        C. that                  D. it

Fill in each numbered blank with a suitable word :

The continent of Antarctica is (1) a huge place that if it (2) a country, it'd be the tsecond biggest in the world, after Russia. It never gets warm there.It is (3) cold in eastern Antarctica that even the summer temperature is lower (4) your freezer at home. Although much of Antarctica consists (5) ice, there is solid rock under it. The ice is so deep and heavy, howerver,(6) it has pushed the earth down. If all that ice melted, the land (7) start to ríse as much as 500 metres. Scientists believe the ice is already melting, and if it continues, the world's seaa and oceans will rise by (8) to 60 meters. They say we must take action now, so (9) to advoid a globad disaster. We need to use less fuel like oil ang gas in (10) to reduce the effect of global warming on Antarctica's ice.

Fill in each blank with a suitable word :George Washington was born on February 22^nd 1732 in Virginia. His (1) were Augustin and Mary Washington. George (2) up on a farm in virginic. Little is (3) of his early chilhood. He attended (4) irregularly from his 7^th to his 15^th year. His (5) subject was mathematics. He learned to be ra surveyor of land when he grew up. He (6) the army and was a leader during the American Revolution. He later became the first (7) of the United states. George Washington is (8) by his people the "Father of our country". The Americans (9) his birthday on Presidents'Day in February. His (10) is on the one dolllar bill.

rewrite the sentence,begin as shown,so that the meaning stays the same :He speaks Russian better than we do=> We are not ....

tìm GTNN hoặc GTLN của :

A = a² + b² + c² - ab -ac - bc +3

với a+b+c = 1

B = 5x - 6x2

tìm GTNN hoặc GTLN của :

A = a² + b² + c² - ab -ac - bc +3

B = 5x - 6x²

Tìm số nguyên dương x, y thoả mãn :

2^x + (x² + 1)(y² - 6y + 8 ) = 0