3A = 3² + 3³ + 3⁴ + ... +3²⁰⁰⁷

=> 3A - A = 2A = 3²⁰⁰⁷ - 3¹ = 3( 3²⁰⁰⁶-1)

=>A = \(\frac{3\left(3^{2006}-1\right)}{2}\)

Ta có : 2A + 3 = 3²⁰⁰⁷ + 3 - 3 

                      =  3²⁰⁰⁷ = 3^x

                     =>  x= 2007

b) 

A = \(\frac{1.5.6+2^3.1.5.6+4^3.1.5.6+9^3.1.5.6}{1.3.5+2^3.1.3.5+4^3.1.3.5+9^3.1.3.5}\)= \(\frac{1.5.6\left(1+2^3+4^3+9^3\right)}{1.3.5\left(1+2^3+4^3+9^3\right)}\)=2

Choose the option among A, B, C, D which needs correcting to make a complete sentence

The camp on the inhospitable, (A) mosquito-infested banks of the River Sekonyer, was (B) set up to track the primates and (C) learn from their habitat, (D) diet and behavior

A. mosquito-infested

B. set up

C. learn from

D. diet and behavior

Có bao nhiêu phát biểu dưới đây là sai khi nói về giao phối ngẫu nhiên?

1. Giao phối ngẫu nhiên không làm biến đổi thành phần kiểu gen và tần số tương đối của các alen trong quần thể

2. Giao phối ngẫu nhiên tạo ra các biến dị tổ hợp, góp phần trung hòa tính có hại của đột biến

3. Giao phối ngẫu nhiên tạo ra các kiểu gen mới, cung cấp nguyên liệu sơ cấp cho quá trình tiến hóa

4. Giao phối ngẫu nhiên không phải là một nhân tố tiến hóa

A.4

B.2

C.3

D.1

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 35 to 44.

         Reference books are not designed to be read from the first page to the last but rather to be consulted to answer the questions and provide both general and specific pieces of information.

         One of the most (35) ______ used reference books is a dictionary, which provides information about words. It lists meanings and spellings, (36) ______ how a word is pronounced, gives (37) ______ of how it is used, may reveal its origins and also lists synonyms and (38) ______. To help you find the words faster, there are guide words at the top of each page showing the first and last words on that page and of course it (39) ______ to know the alphabet!

         There may be numerous special sections at the back with (40) ______ about famous people and places, lists of dates and scientific names, etc. There is usually a section at the front (41) ______ how to use the dictionary, which includes the special abbreviations or signs.

         An atlas is also a reference book and (42) ______ charts, tables and geographical facts, as well as maps. Political maps locate countries and cities, physical maps show the formation of the land with its mountains and valleys, and economic maps show industries and agriculture. To find a specific place, you need to look in the (43) ______ at the back of the atlas and the exact position on the map. There are numerous map (44) ______ that you need to know in order to be able to read a map-almost like a special language-and these are explained at the front of the atlas.

Điền vào ô 43

A. foreword

B. Preface

C. complement

D. index

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 35 to 44.

         Reference books are not designed to be read from the first page to the last but rather to be consulted to answer the questions and provide both general and specific pieces of information.

         One of the most (35) ______ used reference books is a dictionary, which provides information about words. It lists meanings and spellings, (36) ______ how a word is pronounced, gives (37) ______ of how it is used, may reveal its origins and also lists synonyms and (38) ______. To help you find the words faster, there are guide words at the top of each page showing the first and last words on that page and of course it (39) ______ to know the alphabet!

         There may be numerous special sections at the back with (40) ______ about famous people and places, lists of dates and scientific names, etc. There is usually a section at the front (41) ______ how to use the dictionary, which includes the special abbreviations or signs.

         An atlas is also a reference book and (42) ______ charts, tables and geographical facts, as well as maps. Political maps locate countries and cities, physical maps show the formation of the land with its mountains and valleys, and economic maps show industries and agriculture. To find a specific place, you need to look in the (43) ______ at the back of the atlas and the exact position on the map. There are numerous map (44) ______ that you need to know in order to be able to read a map-almost like a special language-and these are explained at the front of the atlas.

Điền vào ô 39

A. assists

B. Pays

C. helps 

D. works

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 35 to 44.

         Reference books are not designed to be read from the first page to the last but rather to be consulted to answer the questions and provide both general and specific pieces of information.

         One of the most (35) ______ used reference books is a dictionary, which provides information about words. It lists meanings and spellings, (36) ______ how a word is pronounced, gives (37) ______ of how it is used, may reveal its origins and also lists synonyms and (38) ______. To help you find the words faster, there are guide words at the top of each page showing the first and last words on that page and of course it (39) ______ to know the alphabet!

         There may be numerous special sections at the back with (40) ______ about famous people and places, lists of dates and scientific names, etc. There is usually a section at the front (41) ______ how to use the dictionary, which includes the special abbreviations or signs.

         An atlas is also a reference book and (42) ______ charts, tables and geographical facts, as well as maps. Political maps locate countries and cities, physical maps show the formation of the land with its mountains and valleys, and economic maps show industries and agriculture. To find a specific place, you need to look in the (43) ______ at the back of the atlas and the exact position on the map. There are numerous map (44) ______ that you need to know in order to be able to read a map-almost like a special language-and these are explained at the front of the atlas.

Điền vào ô 36

A. speaks

B. tells

C. says

D.  gives

Cho 11,25 gam C₂H₅NH₂ tác dụng với 200 ml dung dịch HCl a(M). Sau khi phản ứng hoàn toàn thu được dung dịch có chứa 22,2 gam chất tan. Giá trị của a là

A. 1,3M

B. 1,5M

C. 1,25M

D. 1,36M

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.

Alexis de Tocqueville, the French political scientist, historian, philosopher and politician, is most famous for a four-volume book he wrote called “Democracy in America”. He came to America in 1831 to study the American form of democracy and what it might mean to the rest of the world. After a visit of only nine months, he wrote a remarkable book which is regarded as a classic. De Tocqueville had unusual powers of observation. He described not only the democratic system of government and how it operated, but also its effect on how Americans think, feel, and act. Many scholars believe he had a deeper understanding of traditional American beliefs and values than anyone else who has written about the United States. What is so remarkable is that many of these traits which he observed nearly 200 years ago, are still visible and meaningful today. His observations are also important because the timing of his visit, the 1830s, was before America was industrialized. This was the era of the small farmer, the small businessman, and the settling of the western frontier. It was the period of history when the traditional values of the new country were newly established. In just a generation, some 40 years since the adoption of the U.S. Constitution, the new form of government had already produced a society of people with unique values. He was, however, a neutral observer and saw both the good and bad sides of these qualities.

The first part of “Democracy in America” was written in 1831-32 and published in 1835. A highly positive and optimistic account of American government and society, the book was very well received. He attempted to get a glimpse of the essence of American society, all the while promoting his own philosophy: the equaling of the classes and the inevitable depth of aristocratic privilege. The rest of the book he labored on for four years, and in 1840 the second part was published. This was substantially more pessimistic than the first, warning of the dangers despotism and governmental centralization, and applying his ideas and criticisms more directly to France. As a result, it was not received as well as the first part, except in England where it was acclaimed highly.

Question:According to the passage, “Democracy in America” consisted of how many volumes?

A. three

B.one

C.two

D. four