31.

\(\Leftrightarrow\int\limits^{\dfrac{\pi}{4}}_0log_a\left(1+tanx\right)dx-\dfrac{1}{4}\int\limits^{\dfrac{\pi}{4}}_0dx\ge0\)

\(\Leftrightarrow\int\limits^{\dfrac{\pi}{4}}_0log_a\dfrac{1+tanx}{\sqrt[4]{a}}dx\ge0\)

\(\Leftrightarrow log_a\dfrac{1+tanx}{\sqrt[4]{a}}\ge0\) ; \(\forall x\in\left[0;\dfrac{\pi}{4}\right]\)

\(\Leftrightarrow\dfrac{1+tanx}{\sqrt[4]{a}}\ge1;\forall x\in\left[0;\dfrac{\pi}{4}\right]\)

\(\Leftrightarrow\sqrt[4]{a}\le\min\limits_{\left[0;\dfrac{\pi}{4}\right]}\left(1+tanx\right)=1\)

\(\Rightarrow a\le1\)

Ko tồn tại a thuộc khoảng đã cho thỏa mãn

29.

\(f'\left(x\right)=\dfrac{f\left(x\right)+x+1}{x+1}\)

\(\Rightarrow\left(x+1\right).f'\left(x\right)-f\left(x\right)=x+1\)

\(\Rightarrow\dfrac{f'\left(x\right)}{x+1}-\dfrac{1}{\left(x+1\right)^2}.f\left(x\right)=\dfrac{1}{x+1}\)

\(\Rightarrow\left[\dfrac{f\left(x\right)}{x+1}\right]'=\dfrac{1}{x+1}\)

\(\Rightarrow\dfrac{f\left(x\right)}{x+1}=ln\left|x+1\right|+C\)

\(f\left(1\right)=ln4=2ln2\Rightarrow\dfrac{f\left(1\right)}{2}=ln2+C\Rightarrow C=0\)

\(\Rightarrow f\left(x\right)=\left(x+1\right).ln\left|x+1\right|\)

\(\Rightarrow f\left(3\right)=4ln4=8ln2\)

D. Ribôxôm ti thể khác với ribôxôm của tế bào chất.

D. Ribôxôm ti thể khác với ribôxôm của tế bào chất.

a. from

Chọn A nhé

protect sb/st from Ving: bảo vệ ai/cái gì khỏi cái gì

1. Set đồ năng động: Áo thun cotton + Quần short kaki + Giày thể thao
2. Váy maxi: Váy maxi chất liệu nhẹ nhàng, họa tiết hoa nhí + Sandal
3. Set đồ cá tính: Áo croptop + Quần jean + Áo khoác bomber + Giày sneaker
4. Bộ jumpsuit: Jumpsuit cotton + Sandal
5. Set đồ nữ tính: Áo blouse + Chân váy midi + Sandal cao gót

Con xin chúc tất cả các bạn nữ, những cô giáo luôn hạnh phúc, tràn ngập sức sống và luôn được yêu thương, <3

Con mong:...

Con mong các cô giáo trẻ mãi không già để luôn truyền đạt những kiến thức, hiểu biết cho con!

Con mong các bạn nữ luôn xinh đẹp, trẻ trung để bầu bạn và thấu hiểu con!

Ngày 8/3 là ngày phụ nữ được yêu thương!

Exercise 1. Complete the sentences.

1.

A: Are you working on Monday?

B: No, I’m on holiday.

2.

A: Are you...going......  on holiday this year?

B: Yes, I’m going camping.

3.

A: Did you have a good......time....  in Greece?

B: Yes, it was wonderful.

4.

A: Are you flying to Italy?

B: No, I’m going......by.  train 

5.

A: I’m going to New York next week.

B: Great! Please....send......  me a postcard.

Exercise 2. What type of holiday is each person talking about? (Những người dưới đây đang nhắc đến loại kì nghỉ nào)

1. It was fun but the tent was very small. camping

2. Everything was included – hotels and flights....a package holiday......... 

3. We were on the coach for seven days. I was very tired....a coach tour...... 

4. We walked about 20 kilometres every day.....a walking holiday.... 

5. We went to Switzerland in December. There was a lot of snow. ......a winter holiday..

Exercise 2. Complete the sentences using the following verbs in the correct form:

1. Mozart wrote more than 600 pieces of music.

2. Phuong ..had........a good vacation in Da Lat last year. 

3. I went to Nha Trang last week.  I .....went.. for the sunshine, but it ....rained... every day. So I couldn’t get a tan.

4. Dave ....went..... skiing this morning and unfortunately broke his leg.

5. Yesterday ....was.. awful because I ...failed.. the exam.

6. Ngan ...spent... all her money 2 days ago. It’s understandable because she ...tried..... to make money from gambling (đánh bạc) in Las Vegas.  

Exercise 3. You ask James about his holiday. Write your questions. 

Hi. How are things?

Fine, thanks. I’ve just had a great holiday.

1. Where did you go?

To the U.S. We went on a trip from San Francisco to Denver. 

2. How ..did you go there...? By car?

Yes, we hired a car in San Francisco.

3. It’s a long way to drive. How long .did it take... to get to Denver?

Two weeks.

4. Where ...did you stay..? In hotels?

Yes, small hotels or motels. 

5. ....Was it.. good?

Yes, but it was very hot – sometimes too hot.

6.....Did you visit..the Grand Canyon?

Of course. It was wonderful.