I/ supply the correct verb tense

1. I ( see)..........SAW....a terrible accident on my way to work yesterday

2. My grandma (live)........LIVED...on a farm when she ........WAS........(be) young

3. There ( not be)........WASN'T... electricity in my home town 100 years ago

4. Our parents (have).....WILL HAVE...... a picnic to the countryside next month

5. Her parents ( not come) ...DIDN'T COME...... to her birthday party last Sunday

6. .......DID ......she ( forget)...FORGET...... to do het math homework yesterday?

7. The last time i (go)......WENT...to Paris (be).....WAS.......in 1999

8. There (be)........WERE..more than 100 people at the party last night

9. Why..........DID.......you (come)......COME...home so late yesterday?

10. Many college and university students (wear).....WORE...jeans in the 1960s

11. We ( not study) ........DIDN'T STUDY...hard last school year

12. They (live) ......HAVE LIVED.....in HCM city since 1975

13. My father ( just come)....HAS JUST COME.....back from Singapore

14. .........HAVE......you ( ever visit) ........EVER VISITED...Nha Trang ?

15. Those boys (not finish)....HAVEN'T FINISHED..... their homework yet

16. My mother (teach) .......HAS TAUGHT.....at this school for over twenty years

1. She has not came back to her hometown for 4 years.

2. He has worked as a bank clerk for 3 months.

3. I has just cut my hair since november.

4. We have not called each other for 5 month.

5. When have you had it?

\(:>>\)

III/ fill in the blank with Since or For

1. My sister has been in HaNoi ...since..........last Sunday

2. We haven't seen her......since.... Last January

3. We have read this book.....since.......5 o'clock

4. I have known him......since......we were at the high school

5. They have played football.....since.... 9 a.m

6. Linda went to work in Pairs two years ago, and we haven't seen her......since then.....

III/ rewrite these sentences, using present perfect tense

1. She began to learn English 3 years ago

->she has learned English for 3 years

2. He started playing tennis when he was 6

-> he has played tennis since he was 6

3. He began to work for this company in 2002

-> my brother has worked for this company since 2002

4. He started collecting stamps 4 months ago

-> he has collected stamps for 4 months

5. The last time i saw him was 2 weeks ago

-> i haven't seen him for 2 weeks

6. The last time they visited Hue was in 1999

-> they haven't visited Hue since 1999

7. We last ate in that restaurant in January

-> we haven't eaten in that restaurant since January

8. She last came here 3 months ago

-> she hasn't come here for 3 months

9. It's a long time since i last wrote to her

-> i haven't written to her for a long time

10. It's many years since we last our aunt

-> we haven't met our aunt for many years

III/ rewrite these sentences, using present perfect tense

1. She began to learn English 3 years ago

->she has..learned English for 3 years.

2. He started playing tennis when he was 6

-> he has.played tennis since he was 6.

3. He began to work for this company in 2002

-> my brother has..worked for this company since 2002..

4. He started collecting stamps 4 months ago

-> he has.collected stamps for 4 months..

5. The last time i saw him was 2 weeks ago

-> i haven't.seen him for 2 weeks..

6. The last time they visited Hue was in 1999

-> they haven't.visited Hue since 1999..

7. We last ate in that restaurant in January

-> we haven't .eaten in that restaurant since January..

8. She last came here 3 months ago

-> she hasn't come here for 3 months

9. It's a long time since i last wrote to her

-> i haven't written to her for a long time

10. It's many years since we last our aunt

-> we haven't met our aunt for many years

PTHH: \(Al_2O_3+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2O\)

Ta có: \(\left\{{}\begin{matrix}m_{H_2SO_4}=588\cdot5\%=29,4\left(g\right)\Rightarrow n_{H_2SO_4}=\dfrac{29,4}{98}=0,3\left(mol\right)\\n_{Al_2O_3}=\dfrac{20,4}{102}=0,2\left(mol\right)\end{matrix}\right.\)

Xét tỉ lệ: \(\dfrac{0,2}{1}>\dfrac{0,3}{3}\) \(\Rightarrow\) Al₂O₃ còn dư

\(\Rightarrow n_{Al_2\left(SO_4\right)_3}=0,1\left(mol\right)=n_{Al_2O_3\left(dư\right)}\)

\(\Rightarrow C\%_{Al_2\left(SO_4\right)_3}=\dfrac{0,1\cdot342}{20,4+588-0,1\cdot102}\cdot100\%\approx5,72\%\)

II/ use the correct tense of the verb in brackets

1. I (meet).......met......him at a party last night

2. Charles and i are old friends. I( know )........have known....him since i was in high school

3. When she came home, i (talk)......was talking.....to my mother on the phone

4. I wish i (buy)....didn't buy.......everything i wanted all the time

5. Can you (describe).......describe....... The woman you saw?

6. She (meet).......met..... By her cousin and a couple of her friends

7. These letter can (mail).......mail....at the corner

8. The weather (not be) ........isn't.....nice and warm today

9. Tom (work).......has worked.......in this company for five years

10. You Have your washing machine (repair).......to repair....... Because it doesn't work

\(d,ĐK:x\ge1\\ PT\Leftrightarrow\sqrt{x-1}=2+\sqrt{x+1}\\ \Leftrightarrow x-1=2+x+1+4\sqrt{x+1}\\ \Leftrightarrow4\sqrt{x+1}=-4\Leftrightarrow x\in\varnothing\left(4\sqrt{x+1}\ge0\right)\\ g,ĐK:x\ge\dfrac{1}{2}\\ PT\Leftrightarrow x+\sqrt{2x-1}+x-\sqrt{2x-1}+2\sqrt{\left(x+\sqrt{2x-1}\right)\left(x-\sqrt{2x-1}\right)}=2\\ \Leftrightarrow2x+2\sqrt{x^2-2x+1}=2\\ \Leftrightarrow\sqrt{\left(x-1\right)^2}=\dfrac{2-2x}{2}=1-x\\ \Leftrightarrow\left|x-1\right|=1-x\\ \Leftrightarrow\left[{}\begin{matrix}x-1=1-x\left(x\ge1\right)\\x-1=x-1\left(x< 1\right)\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\left(tm\right)\\x\in R\end{matrix}\right.\)