Cho cấp số nhân a n với a 1 = sin α , a 2 = cos α , a 3 = tan α với α  nào đó. Tính n sao cho  a n = 1 + cos α

A. 5.

B. 6

C. 7.

D. 8

3215  tick nha mình đầu tiên

Read the following passage and mark the letter A, B, C, or D to indicate the correct word or phrase that best fits each of the numbered blanks.

Computers cannot make mistakes. Stories have been heard sometimes about computers paying people too much money or sending them (1)_____ for things they didn’t buy. These mistakes ae made by the programs. Some years ago an American computer-controlled rocket went (2)____ and had to be destroyed. The accident has been caused by a small mistake in one line of the program, which (3)______ the USA 18 million dollars. Criminals have found that “computer (4)_____ are a lot easier than robbing a bank.” Hundreds of millions of dollars are stolen from businesses every year by people (8)______ the information in computers.

Question 4.

A. robberies

B. burglaries

C. thieves

D. crimes

Cho 3,84g Cu phản ứng với 80ml dung dịch chứa HNO 3  1M và H 2 SO 4  0,5M thấy thoát ra V(l) NO ở (đktc) là sản phẩm khử duy nhất. Tìm V ?

A. 0,448.

B. 0,896.

C. 1,792.

D. 1,344.

1) chơi cờ

2) con cua

3) đua xe

a)

3x : 2,7 = \(\dfrac{1}{3}:2\dfrac{1}{4}=\dfrac{1}{3}:\dfrac{9}{4}=\dfrac{1}{3}.\dfrac{4}{9}=\dfrac{4}{27}\)

=> 3x = \(\dfrac{4}{27}\). 2,7 =\(\dfrac{1028}{270}=4\)

=> x = 4 : 3 = 1,333...