\(\left(x^2-2x+2\right)\left(x^2-2\right)\left(x^2+2x+2\right)\left(x^2+2\right)\)

\(=\left[\left(x^2-2x+2\right)\left(x^2+2x+2\right)\right].\left[\left(x^2-2\right)\left(x^2+2\right)\right]\)

\(=\left(x^4-4x^2\right)\left(x^4-4\right)\)

a, \(a^2+b^2=\left(a+b\right)^2-2ab\)

Thay a+b=s; ab vào đa thức trên ta được:

\(\left(a+b\right)^2-2ab=s^2-2p\)

b, \(a^3+b^3=\left(a+b\right)^3+3a^2b-3ab^2\)

\(=\left(a+b\right)^3-3ab.\left(a+b\right)\)

Thay a+b=s; ab=p Ta được:

\(\left(a+b\right)^3-3ab.\left(a+b\right)=s^3-3sp\)

c, \(a^4+b^4=\left(x^2+y^2\right)^2-2x^2y^2\)

\(=\left(s^2-2p\right)^2-2p^2=s^4-4s^2p+2p^2\)

CHÚC HỌC TỐT!!

đòi hỏi thế

The name of my best friend is Oanh. She is my good friend and cares for me a lot. She behaves me well and helps always. I met her in class 6 and became best friend. She is my true friend because she understands me very well and cares for my every need. I like her very much. I never had any friend like her ever before. She comes to my home and I too go to her home. Our parents respects us very much and like our friendship. She is so precious for me and I never want to lose her. Whenever I get absent in the classroom, she helps me in doing all the left home works and class works.

She is much similar to me in many aspects. She never argues me and describes me well anything which I get stuck. She is an open minded girl and never feels bad for my misbehave. She is very entertaining in nature and makes me laugh through her interesting jokes and talks in the spare time. She is very cute and attractive, attracts everyone through her smile and nice way of talk. She promotes me always to do better in the classroom and exams. We are good in sports and academic activities. She takes my opinions in her every tough work to do in the right way. We manage to share things in our difficult times. We always perform better in the class tests and main exams.

Last summer, I went to Cua lo with my family. We went there by car, it is very far from my house, it is about 400 km, so we were very tired, but at one we felt better when we saw the sea.

Cua lo beach is really interesting, the beach is very large, flat, and it has a lot of sand. Waves are very strong, you will be very excited when you play with it. There are a lot of beauty spots, and good seafood there

We stayed in Binh Minh hotel. It was a very nice and comfortable hotel, it’s also rather near the sea.

The weather was hot and sunny all day. The sea was cool and clear, because it was very windy in the afternoon. We went swimming twice a day. My children was excited about it. The food was extremely delicious but not very expensive.

We took a lot of Photograps of the sea, bought a lot of seafood especially octopus and some sea present for our relatives.

After a week in Cua lo beach we felt happy and stronger.

We hope to go there again.

Hello! Nice to meet you! Now, I very happy to introduce my self. My name is Phuong Anh. Please call me Anh. I'm 13 years old and I am a student at Thanh Ha Secondary School. I'm in grade 8, class 8a. I was born in Thanh Long. My family has 4 peaple: my mother, father, sister and me. My father and My mother are teacher. And my sister is a student. I like English very much but I don't good at it. I hope I try my best to learn English now. I think I speak English very well! Now, I study very hard because in the future, I want to be a doctor! In my free time, I usually watch TV or read books, listen to music. On my weekend, sometimes, I go to camping with my family or go to the movie theater. In short, I very happy with my life. Of course, I will make it happier!!!

Tham khao nak

Bài 1:

Vì \(AH\perp BD;CK\perp BD\)

\(\Rightarrow\) AH//CK(1)

Xét \(\Delta ABD\) và \(\Delta BCD\) có:

AB=CD(ABCD là hình bình hành)

\(\widehat{A}=\widehat{C}\) (góc đối bằng nhau)

AD=BC(ABCD là hình bình hành)

\(\Rightarrow\Delta ABD=\Delta CBD\left(c.g.c\right)\)

\(\Rightarrow\) Đường cao AH và CK bằng nhau(2)

Từ (1) và (2) suy ra AHCK là hình bình hành.

Bài 2:

Xét ΔABC, ta có :

EA = EB (gt)

FB = FC (gt)

=> EF là đường trung bình

=> EF = AC : 2 VÀ EF // AC. (1)

Cmtt, ta được : HG = AC : 2 VÀ HG // AC. (2)

Từ (1) và (2), suy ra : HG = EF và HG // EF

=> tứ giác EFGH là hình bình hành.

Chúc bạn hk tốt!!

Vì DE//AB; EF//BD

\(\Rightarrow\) Tứ giác FEBD là hình bình hành.

Theo tính chất của hình bình hành. Ta có:

BF=DE(cặp cạnh đối bằng nhau)

Mà AB//ED\(\Rightarrow\) \(\widehat{BAD}=\widehat{ADE}\) (SLT)

Mặt khác:\(\widehat{BAD}=\widehat{DAE}\Rightarrow\widehat{DAE}=\widehat{ADE}\Rightarrow\Delta AED\) cân tại E

\(\Rightarrow AE=DE\)

Mà: \(AE=DE=BF\)

Vậy \(AE=BF\left(đpcm\right)\)

Số số hạng của biểu thức là :

( 100 - 1 ) : 1 + 1 = 100 ( số hạng )

Tổng của biểu thức là :

( 100 + 1 ) x 100 : 2 = 5050

Đ/s: ...