Cho hình chóp S.ABC có SA=a, SB=b, SC=c. Một mặt phẳng (α) đi qua trọng tâm của tam giác ABC, cắt các cạnh SA, SB, SC lần lượt tại A’, B’, C’. Tìm giá trị nhỏ nhất của  1 S A ' 2 + 1 S B ' 2 + 1 S C ' 2

A.  3 a 2 + b 2 + c 2 .

B.  2 a 2 + b 2 + c 2 .

C.  2 a 2 + b 2 + c 2 .

D.  9 a 2 + b 2 + c 2 .  

Chọn câu đúng.

A.  31 2 . 32 2 . 33 2 . . . 60 2 = 1 . 2 . 3 . 4 . 5 . 6 . 7 . . . 60

B.  31 2 . 32 2 . 33 2 . . . 60 2 = 1 . 3 . 5 . 7 . . . 59

C.  31 2 . 32 2 . 33 2 . . . 60 2 = 1 . 3 . 5 . 7 . . . 60

D.  31 2 . 32 2 . 33 2 . . . 60 2 = 2 . 4 . 6 . 8 . . . 60

Tác phẩm Lục Vân Tiên ta hiểu được sự đối lập thiện – ác và niềm tin của tác giả vào những điều tốt đẹp ở đời. Tìm hiểu, đánh giá nghệ thuật kết cấu và nghệ thuật ngôn từ của đoạn thơ này, đúng hay sai?

A. Đúng

B. Sai

Clo hoá PVC thu được một polime chứa 63,96% clo về khối lượng, trung bình 1 phân tử clo phản ứng với k mắt xích trong mạch PVC. Giá trị của k là

A. 5

B. 6

C. 4

D. 3

Loại tơ nào sau đây được điều chế bằng phản ứng trùng hợp

A. Tơ nitron

B. Tơ visco

C. Tơ xenlulozơ axetat

D. Tơ nilon-6,6

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

Do you ever wish you were more optimistic, someone who always (45)____ to be successful? Having someone around who always fears the worst isn't really a lot of (46)____ - we all know someone who sees a single cloud on a sunny day and says, 'It looks like rain.' But if you catch yourself thinking such things, it's important to do something about it.

You can change your view of life, according to psychologist. It only takes a little (47)___, and you'll find life more rewarding as a (48)____. Optimism, they say, is partly about self-respect and confidence but it's also a more positive way of looking at life and all it has to (49)____. Optimists are more (50)_____ to start new projects and are generally more prepared to take risks.

Upbringing is obviously very important in forming your (51)___ to the world. Some people are brought up to depend too much on others and grow up forever blaming other people when anything (52)____ wrong. Most optimists, on the (53)____ hand, have been brought up not to (54)____ failure as the end of the world - they just get on with their lives.

Điền vào ô 46

A. amusement

B. play

C. enjoyment

D. fun

Read the following passage and mark the letter A, B, C, or D on your answer sheet to choose the word or phrase that best fits each of the numbered blanks from 25 to 29. Fill in the appropriate word in question 25

Reasons to Not Hit Your Kids

  The practice of hitting children teaches them to become hitters themselves. Extensive research data is now available to support the direct correlation (25)_______corporal punishment in childhood and violent behavior in the teenage and adult years. Virtually, all of the most dangerous criminals (26)_____regularly threatened and punished in childhood.

  Punishment gives the message that "might make right," that it is okay to hurt someone smaller and less powerful than you are. The child then feels it is appropriate to mistreat younger or smaller children, and when he becomes an adult, feels little (27)______for those less fortunate or powerful than he is, and fears those who are more so. Thus it is difficult for him to find (28)_______friendships.

  Children learn best through parental modeling. Punishment gives the message that hitting is an appropriate way to express one's feelings and to solve problems. If the child rarely sees the parents handle anger and solve problems in a creative and positive way, he can never learn how (29)______that himself. Thus inadequate parenting continues into the next generation.

(Adapted from "Reasons to Not Hit Your Kids" by Jan Hunt)

A. among

B. about

C. between

D. above