Cho hình chóp tứ giác đều S.ABCD có đáy ABCD là hình vuông tâm O. Khoảng cách từ điểm O đến mặt phẳng (SCD) bằng a 14 7  và góc giữa đường thẳng SB với mặt đáy bằng 60°. Tính thể tích V của khối chóp S.ABC theo a.

A. V = 3 a 3 2 2

B. V = 3 a 3 2 4

C. V = 3 a 3 2 16

D. V = 9 a 3 2 4

Read the following passage and choose the best answer for each blank. Building Confidence in Teens

 Confidence is one's belief in their own ability. Confident people rationally believe they are (26) _______ of doing things well and therefore aren't afraid to do those things or even (27)_______new things. Teens who are confident to grow up have a good (28) _______ of self and become happy adults. Parents can help teens (29) ______  their confidence throughout their adolescence by following these tips: Be trustworthy. Be there when your teen needs you. Provide a safe home environment and firm but fair discipline. This is a (30)_______that your teen's confidence can stand on. Give your teen choices. One of the things that confidence helps teens do is making a decision. You can help teens make decision by (31) _______ them choices as often as possible. (32)_______your teen to try new things. Be available to take them where they need to go and do so without complaining. Become your teen’s biggest fan, (33) _______ it is in sports, or in school. Allow your teen to fail, do not fix their problems for them. If they need you to help talk the problem through, ask open ended questions so that they (34) _______ to their own conclusions. Praise your teen when praise is suitable. We know that too much praise is not good _______(35) , but suitable praise is necessary for your teen's self-confidence.

Question 28:

A. feeling

B. state

C. sense

D. ability

Read the following passage and choose the best answer for each blank. Building Confidence in Teens

 Confidence is one's belief in their own ability. Confident people rationally believe they are (26) _______ of doing things well and therefore aren't afraid to do those things or even (27)_______new things. Teens who are confident to grow up have a good (28) _______ of self and become happy adults. Parents can help teens (29) ______  their confidence throughout their adolescence by following these tips: Be trustworthy. Be there when your teen needs you. Provide a safe home environment and firm but fair discipline. This is a (30)_______that your teen's confidence can stand on. Give your teen choices. One of the things that confidence helps teens do is making a decision. You can help teens make decision by (31) _______ them choices as often as possible. (32)_______your teen to try new things. Be available to take them where they need to go and do so without complaining. Become your teen’s biggest fan, (33) _______ it is in sports, or in school. Allow your teen to fail, do not fix their problems for them. If they need you to help talk the problem through, ask open ended questions so that they (34) _______ to their own conclusions. Praise your teen when praise is suitable. We know that too much praise is not good _______(35) , but suitable praise is necessary for your teen's self-confidence.

Question 35:

A. neither

B. together

C. either

D. whether

Cho Δ ABC. Tia phân giác góc trong của góc A cắt BC tại D. Cho AB = 6, AC = x, BD = 9, BC = 21. Tính kết quả đúng của độ dài cạnh x

A. x = 14   

B. x = 12 

C. x = 8   

D. x = 6