Bài 3: cho tức giác ABCD có AB=BC,CD=DA

a) chứng minh BD vuông góc với AC

b) tính góc A , góc C biết góc B=100 độ góc D=50 độ

có hình vẽ và k làm tắt các bước hay ghi chứng minh tương tự như câu... ạ 

Cho tam giác ABC vuông tại A, đường cao AH. Biết AB = 24 , AC = 25 TÍNH AH , BH , CH

B7: Cho tam giác ABC có ba góc đều nhọn, AH vuông góc với BC tại H. Trên tia đối của tia HA lấy điểm D sao cho HA=HD

a) C/M: BC và CB lần lượt là các tia phân giác của các góc ABD và ACD.

b) C/M: CA = CD và BD = BA

c) Cho góc ACB=45 độ. Tính góc ADC.

d) Đường vuông góc AH phải có thêm điều kiện gì thì AB//CD?

The distance between Hai Phong and Ha Noi is about 120km.   

 ->It’s..............................................................................................................................

They will use renewable energy in the future.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             

→ Renewable energy .....................................................................................................

Viết phương trình phản ứng có sự di chuyển electron khi cho:
a) Kali tác dụng với khí clor.
b) Magie tác dụng với khí oxy.
c) Natri tác dụng với lưu huỳnh.
d) Nhôm tác dụng với khí oxy.
e) Canxi tác dụng với lưu huỳnh. 
f) Magie tác dụng với khí clor.

Fill in the blank with a suitable word.

        open     forget   come     be           bring     have      turn       wait       make                                                                                                                                                                                                               Dear John,

      Come and see me next weekend. I’m staying in a house by the sea. Don’t (l)    __to ring your swimming costume with you! It isn’t difficult to find the house. When you get to the crossroads in the town, (2)        ___ right and drive to the end of the road. (3)        careful because it is a dangerous road! (4)                  some warm clothes with you because it is cold in the evenings here. If I am not at home when you arrive, don’t (5)         for me. The key to the house is under the big white stone in the garden. (6)              the front door and (7) _____ yourself a cup of tea in the kitchen! (8)                         a good journey!                      Best wishes,                Vinh

cho d: y=-x+5. tìm tọa độ giao điểm của M,N trên d với trục tung và trục hoành.

10. Minh’s tooth hurt _____ he has a cavity.( but / and / or / because)
11.It is an _____book .(interest / interested / interesting / interestingly)
12.How _________does the T.V cost ?(far /long/ often / much)
13.What ______you doing now ? _ I am washing my clothes (are / do/ does/ were)
14.I’m not a teacher and _________ is he .(so/ neither / either / too)
15. Nam is a ________ student. He always gets good marks(good/ well /. Bad /badly)

5. Tri Nguyen ________ is a famous place in Nha Trang.
A. Temple B. Museum C. Aquarium D. Pagoda
6. Mrs Anh takes care of people’s hair. She is a ________
A. dressmaker B. hairdresser C. hairmaker D. head
7. Hoa learned how ___ a sewing machine. (use/ using /used/ to use)
8. Ba ________ to school yesterday because he felt tired.
A. doesn’t go B. wasn’t go C. didn’t go D. not went
9. What is his _______ ? – 60 kg(heavy / weighed / weight / height)

I often went to school by bike last year.

-> I used ……………………………………..................................................................

Cho 30g hỗn hợp hai kim loại sắt và đồng tác dụng với dung dịch HCl dư. Sau khi phản ứng xong thu được chất rắn A và 6,72l khí (ở đktc)

a) Viết phương trình phản ứng hóa học xảy ra.

b) Tính thành phần trăm theo khối lượng của hỗn hợp ban đầu.

$\sqrt{48}-6\sqrt{\frac{1}{3}}+\frac{\sqrt{3}-3}{\sqrt{3}}$

Cho hình bình hành ABCD có AD = 2AB, $\hat{A}={60}^0$. Gọi E và F lần lượt là trung điểm của BC và AD

a) Chứng minh $AE \perp BF$

b) Chứng minh tứ giác BFDC là hình thang cân

c) Lấy điểm M đối xứng của A qua B. Chứng minh tứ giác BMCD là hình chứ nhật

d) Chứng minh M,E,D thẳng hàng

Tổng số hạt trong ion R+ là 57. Trong nguyên tử R, số hạt mang điện nhiều hơn số hạt không mang điện là 18 hạt. Xác định tên R, số p, n, e của R. Viết cấu hình e của R, R+. ?

Cho các nguyên tố N, S có điện tích hạt nhân lần lượt là $7^{+}$, ${16}^{+}$, hãy viết cấu hình electron của N, ${\mathrm{N}}^{-3}$ , ${\mathrm{N}}^{+2}$, S, ${\mathrm{S}}^{-2}$, ${\mathrm{S}}^{+4}$

Tìm 20 chữ số tận cùng của 100!

Cho tam giác  DEF vuông tại D có DE =8cm góc E =40 đg cao DH 

a) tính độ dài DF,EF, số đo góc F và đg cao DH 

b) gọi A và B thứ tự là hình chiếu của H trên DE và DF . cm ${\left(\frac{DE}{DF}\right)}^2=\frac{EH}{FH}$

C) CM EF.EA.FB=DH^3