Ta có:

\(x^2+y^2+z^2=y\left(x+z\right)\\ \Leftrightarrow x^2+y^2+z^2-yx-yz=0\\ \Leftrightarrow2x^2+2y^2+2z^2-2yx-2yz=0\\ \Leftrightarrow\left(x-y\right)^2+\left(y-z\right)^2+x^2+z^2=0\\ \Leftrightarrow\left\{{}\begin{matrix}x-y=0\\y-z=0\\x=0\\z=0\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=y\\y=z\\x=0\\z=0\end{matrix}\right.\\ \Leftrightarrow x=y=z=0\)

Đúng thì tích"Đúng" mk với bạn nhé!

Ta có:

\(\left(x-7\right)\left(x-4\right)=0\\ < =>\left[{}\begin{matrix}x-7=0\\x-4=0\end{matrix}\right.\)

\(< =>\left[{}\begin{matrix}x=7\\x=4\end{matrix}\right.\)

Ta có:

\(c^n=1\\ =>n=1\)

\(c^n=0\\ =>n=0\)

\(2^9=2^3.2^3.2^3=8.8.8=512\)

Tính: 

Tìm số lớn nhất trong các số : 4375, 4735, 4537, 4753

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

Brave William Baldock , who is six years old , is a hero after helping his mother when she fell downstairs . William quickly rang for an ambulance when he discovered his mother had broken her leg . In spite of being frightened , he (1)_____ the emergency services what had happened and answered all the questions they asked him. He also telephoned his father at work, and then his grandmother, to explain what he had (2)______. While waiting for these people to arrive, William looked after his 18-month-old sister.

When ambulance man Steve Lyn went to the house , he was amazed: "It's great that a young boy of six knew the right number to deal and was able to give us the correct information.” (3)______ of William's quick thinking , we were able to (4)______ there immediately.

Mrs Baldock left hospital yesterday, very (5)______ to both William and the ambulance service.

Điền vào số 1

A. called

B. talked

C. spoke

D. told

Hạt anpha có khối lượng 6 , 64 . 10 27  kg chuyển động tròn đều trong từ trường đều có cảm ứng từ B = 0,5T. Biết bán kính quỹ đạo là 0,5 m. Tốc độ của hạt là

A.  3 , 8 . 10 7   m / s

B.  7 , 6 . 10 7   m / s

C.  1 , 9 . 10 7   m / s

D.  3 , 8 . 10 6 m / s

Nháy đúp chuột ở biểu tượng  . Tập gõ các phím đã học theo nội dung dưới đây. Chú ý gõ phím cách sau các cụm chữ hoặc kí hiệu.

Find the word which has a different sound in the part underlined.

A. stupid

B. studio

C. study

D. student