cân bằng phương trình oxh khử  4NH3 + 5O2 → 4NO + 6H2O

Cho hình vuông ABCD. M là trung điểm AB. G là trọng tâm △ABD 

a. Tính (AB→+ AD→).(BD→+ BC→)

b. CG→.(CA→+ DM→)

em kh biết ghi ký hiệu vecto nên nhìn hơi rối ạ

 Choose the word/phrase which is closest in meaning to the underlined part of each question. Write A, B, C or D on the answer sheet. (0.4pt)

1. My new piano cost me an arm and a leg.

A. was not beautiful B. was so cheap C. was old D. was very expensive

2. I don’t want to ask her to do anything. She doesn’t lift a finger.

A. is helpful B. is very lazy C. is industrious D. looks cruel