Cho tứ diện đều S.ABC có thể tích là V, độ dài cạnh là a. Trên các cạnh lấy các điểm sao cho . Gọi là thể tích của hình chóp S.MNP. Khi đó giá trị của tính theo a là:  

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Một số câu hỏi khác có thể bạn quan tâm.

• Choose the best answer for the following sentence:

  ____________ young volunteers do the work, such as: cleaning up the houses, doing the shopping and cooking meals for the sick and old people?
  
   

• Choose the best answer for the following sentence:

  Do you think that if you bring __________ to others, you are also a happy person?
   

• Choose the correct sentence which is built from the words and phrases given:

   I / display / my collection of dolls / in a window / arrange them / size
  
  

• Choose the correct sentence which is built from the words and phrases given:

  energy / electricity / can / of / heat / other / be / and / solar / forms / into / as / energy / converted / such
  
  

• Choose one sentence that has the same meaning as the root one:

  Jane made a cake but nobody liked it.
  
  

• Choose one sentence that has the same meaning as the root one:

  I do not like watching TV as TV discourages conversations and prevents creativity.
  
  

• Choose one sentence that has the same meaning as the root one:

  She paints watercolor pictures of flowers as a hobby.
  
  

• Choose one sentence that has the same meaning as the root one:

  I always dream of appearing on stage.
  
  

• Choose one sentence that has the same meaning as the root one:

  They have planted thousands of trees along the new boulevard.
  
  

• Choose the best answer for the following sentence:

  ____________ do many people do volunteer work?