cho tam giác ABC nhọn, ngoài tam giác dựng các hình vuông ABDE và ACFH, dựng hình bình hành AEIR
a/. tam giác ABC = tam giác RIA
b/. CI = BF
c/. CI⊥BC
d/. AI, CF, BD đồng quy

Phân tích các đa thức sau thành nhân tử:
a/ (x² + x)² + 9x² + 18x + 20
b/ x⁴ - 2x² - 400x - 9999

Một vật được móc vào lực kế để đo lực theo phương thẳng đứng. Khi vật ở trong không khí, lực kế chỉ 4,8N. Khi vật chìm trong nước, lực kế chỉ 3,6N . Biết trọng lượng riêng của nước là 10⁴ N/m³. Bỏ qua lực đẩy Acsimet của không khí. Thể tích của vật nặng là bao nhiêu?

Phân tích đa thức sau thành nhân tử:
x(y²+z²)+y(z²+x²)+z(x²+y²)+2xyz

Rewrite the second sentence so that it has a similar meaning to the first one.
1/ It is interesting to learn English.
→ Learning........................................
2/ He failed his exam because he was lazy.
→Because of......................................
3/ He uses all his free time to look after his garden.
→He spends.......................................
4/ Nobody cleaned the floor yesterday.
→The floor.........................................
5/ It is two months since I saw her.
→I haven't..........................................

Combine each pair od sentences to make one sentence, using the words given in brackets.
1/. Lang Lieu couldn't buy any special food. He was very poor. (BECAUSE)
2/. The Hung King Temple Festival was a local festival. It has become a public holiday in VN since 2007. (HOWEVER)
3/. We don't celebrate the festival. It costs too much money. (IF)
4/. The tortoise was running. The hare was sleeping. (WHILE)
5/. The girl worked hard. Her stepmother wasn't happy. (ALTHOUGH)

Choose the correct option for each gap tp complete the sentences.
1/.Using computers too much may have harmful effects ......... your minds and bodies.
A. on B. to C. with D. onto
2/.You should.......... information about a custom or tradition.
A. finds B. found C. finding D. find
3/. In the UK, there are lots of customs for table manners. For example, we....... use a knife and fork at dinner.
A. have to B. are having C. has to D. having
4/. In VN, tou ......... use only the first name to address people older than you.
A. should B. must C. shouldn't D. have to
5/.At the Mid-Autumn Festival, kids can sing, dance, and enjoy moon-cakes;........., every child lkes it very much.
A. However B. Moreover C. Because D. Therefore
6/. In 2010, HN............its 1000^th anniversary.
A. celebrated B. commemorated C. worshipped D. remembered
7/............ spring comes, many Vietnamese villages prepare for a new festival season.
A. While B. When C. Nevertheless D. However
8/.The ........... of quan ho singing has been recognized as a world heritage.
A. preservaton B. procession C. song D. performance
9/.Saint Giong was unable to talk, smile, or walk ....... he was three years old.
A. even though B. because C. while D. if
10/. Lac Long Quan missed his life in the sea;.........., he took 50 sons back there.
A. therefore B. however C. moreover D. otherwise