Hạt nhân X phóng xạ và biến thành một hạt nhân  Y bền. Coi khối lượng của hạt nhân X, Y bằng số khối của chúng tính theo đơn vị u. Biết chất phóng xạ X có chu kì bán rã là T. Ban đầu có một khối lượng chất X, sau 2 chu kì bán rã thì tỉ số giữa khối lượng của chất Y và khối lượng của chất X là:

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Một số câu hỏi khác có thể bạn quan tâm.

• Choose the best answer for the following sentence:

  Ii that the company ______________?
  
  

• Choose the best answer for the following sentence:

  A mouse is a hand - held control that lets you point to and selects items on the ___________.
   

• Choose the best answer for the following sentence:

  Many places of ____________ beauty have beer, produced by computer.
   

• Choose the best answer for the following sentence:

  Computer connected with internet can help us to send and _____________ letters easily.
  
  

• Choose the best answer for the following sentence:

  Computers are used to process information which is called _____________.
  
  

• Choose the best answer for the following sentence:

  When you are tired of hard work, you should listen to __________ music to relax.
   

• Choose the best answer for the following sentence:

  The CPU consists of two other ____________ sub-units: The Control Unit (CU) and
  the Arithmetic-Logical Unit (ALU)
  
  

• Choose the best answer for the following sentence:

  We can now hold long distance meetings ____________ which the participants can
  see each other on a screen.
   

• Choose the best answer for the following sentence:

  Air conditioner is used to keep the air cool or warm ____________ it is hot or cold.
  
  

• Choose the best answer for the following sentence:

  It was the house ____________ my father bought 2 years ago.