1. Megan didn't have to insult Jean's cooking in front of everyone at the party last night. She ( just say )....... she was full or had some salad if she didn't like the meal.

2. Five of committee members will be unable to attend the next meeting. In my opinion, the meeting (postpone)..........

3. New research suggests that exercise (reduce).....the chance of heart disease as well as cancer. That's why I told my father that he (start)......walking once a day.

4. We (call)......Tim before we go over to his house, he (not be)..........there. I don't want to drive all the way there for nothing.

5. Try to speak slowly when you give your speech, if you do not, some of your words (misunderstand)...........

6. Some UFO sightings (not explain).......easily. No one is able to explain them easily.

1.Please, pay a visit to us when you travel to VietNam.

-> Please, come.......

2. Lan has a lot of homework, so she doesn't watch her favorite program on TV.

-> She would.....

3. I'm really sorry. I didn't finish the project on time

-> You should.....

4. Mr.Phong hates lazy people.

-> Mr.Phong doesn't.....

Giải bất phương trình :

\(\frac{3\left(4x^2-9\right)}{\sqrt{3x^2-3}}\le2x+3\)

Cho sin18 = \(\frac{\sqrt{5}-1}{4}\). Tính cos18, sin72, sin162, cos162, sin108, cos108, tan72

Cho tam giác ABC có góc B < 90, AQ và CP là các đường cao, S_ABC = 9 S_BPQ.

a, Tính cosB

b, Cho PQ = 2 \(\sqrt{2}\). Tính bán kính R của đường tròn ngoại tiếp tam giác ABC

Chứng minh đẳng thức sau :

a, \(\left(\frac{tan^2x-1}{2tanx}\right)^2\) - \(\frac{1}{4sin^2x.cos^2x}\) = -1

b, \(\frac{cos^2x-sin^2x}{sin^4x+cos^4x-sin^2x}\) = 1 + tan²x

c, \(\frac{sin^2x}{cosx.\left(1+tanx\right)}-\frac{cos^2x}{sinx.\left(1+cotx\right)}=sinx-cosx\)

d, \(\left(\frac{cosx}{1+sinx}+tanx\right).\left(\frac{sinx}{1+cosx}+cotx\right)=\frac{1}{sinx.cosx}\)

e, cos²x.(cos²x + 2sin²x + sin²x.tan²x) = 1

Với a,b,c > 0. Chứng minh :

\(\frac{a^3b}{c}\) + \(\frac{a^3c}{b}\) + \(\frac{b^3a}{c}\) + \(\frac{b^3c}{a}\) + \(\frac{c^3a}{b}\) + \(\frac{c^3b}{a}\) \(\ge\) 64