I. The simple past or the past continuous tense 1.When I arrived the lecture had already started and the professor (write) ……………… on the overhead projector. 2.I (make) ……………… a cake when the light went out. I had to finish it in the dark. 3.I didn't want to meet Paul so when he entered the room I (leave). ………………. 4.He (watch) ……………… TV when the phone rang. Very unwillingly he (turn) ……………… down the sound and (go) ……………… to answer it. 5.He was very polite. Whenever his wife entered the room he (stand) ……………… up. 6.He always (wear) ……………… a raincoat and (carry) …………… an umbrella when he walked to the office. 7.He suddenly (realize) ……………… that he (travel) ……………… in the wrong direction. 8.When I (look) ……………… for my passport I (find) ……………… this old photograph. 9.You looked very busy when I (see) ……………… you last night. What (you/ do)? ………………. 10.He (clean) …..………… his gun when it accidentally (go) …went…………… off and (kill) ……killed………… him. II. The present perfect or the past simple 1.This is my house. ~ How long (you/ live) here ………………? ~I (live) ……………… here since 1970. 2.He (live) ……………… in London for two years and then (go) ……………… to Edinburgh. 3.Shakespeare (write) ……………… a lot of plays. 4.I (not see) ……………… him for three years. I wonder where he is. 5.When ……………… (he/ arrive)? ~ He (arrive) ……………… at 2.00. 6.I (read) ……………… his books when I was at school. I (enjoy) ……………… them very much. 7.I never (drink) ……………… whisky. ~Well, have some now. 8.The clock is slow. ~ It isn't slow, it (stop) ………………. 9.He (go) ……………… out ten minutes ago. 10.……………… (You/ have) breakfast yet? ~ Yes, I ……………… (have) it at 8.00. 11.……………… (You/ see) the moon last night? 12.The play …………………………… (just/ begin). You are a little late. 13.He (break) ……………… his leg in a skiing accident last year. 14.Mr. Pound is the bank manager. He (be) ……………… here for five years. 15.Where is Tom? - I (not see) ……………… him today, but he (tell) ……………… Mary that he'd be in for dinner.

Biết rằng khi nhiệt phân hoàn toàn magie cacbonat (rắn) thì tạo ra magie oxit (MgO) (rắn) và khí cacbonic (CO2). Người ta đem nhiệt phân 80 gam một mẫu magie cacbonat (MgCO3) đến khối lượng không đổi thì thấy có 30 gam magie oxit và 16,8 lít khí CO2. Tính độ tinh khiết của mẫu magie cacbonat nói trên?

giúp mình với bài này ra một số có mũ

a, x^3+1-x^2-x b, (x+y)^3-x3-y3

CMR:(a-b/c-d)^3=a^3-b^3/c^3-d^3

giúp minhhf bài này với các bạn

a) x mũ 3-16x= 0 b) (2x + 1) mũ 2 - (x - 1) mũ 2 = 0 tìm x ạ

Cali : Cho nick Ai chưa có nhóm vào đây điểm huyệt

khoanh đáp án đúng Why don't you ... to the hospital? * a) going b) go c) went You job is so good. Why did you quit your job? If I were you, I .... that. * a. wouldn't do b. would do c. won't do d. will do You should .... more time with your family. * a) spends b) spend c) spending When I was 5 years old, I used to ..... * a) play football b) playing football c) plays football Now I get used to .... early in the morning * a) waking up b) wake up c) wakes up The tree .... by young people. * a) plant b) plants c) is planted d) are planted The elephant is the ..... animal in the world. * a) larger b) largest c) more largest d) more larger The book ..... I borrowed from you is old. * a) in which b) who c) which The city ..... I live is polluted. * a) who b) which c) where d) in where Alice, ..... is beautiful, is my girlfriend. * a) whom b) that c) who d) which The ants are ...... than the dogs. * a) small b) big c) smaller d) bigger

Cho xOy=37 độ.Tìm số đo góc phụ với nó, nêu cách vẽ góc đó. Cho aOb=120 độ.Tìm số đo góc bù với nó, nêu cách vẽ góc đó.