a: \(A=\dfrac{2x^2+x^2-1-2x^2+2x+1}{x\left(x+1\right)}=\dfrac{x^2+2x}{x\left(x+1\right)}=\dfrac{x+2}{x+1}\)

a: Xét tứ giác ABNC có 

O là trung điểm của AN

O là trung điểm của BC

Do đó: ABNC là hình bình hành

mà \(\widehat{BAC}=90^0\)

nên ABNC là hình chữ nhật

a: Đơn chất: \(H_2;N_2;Cl_2;O_2\)

a: Đơn chất: 

mn giúp mk làm câu b và c chứ ko phải câu a,câu a mk bt làm ròi

đề đâu ????

                                             MY SCHOOL :

My school name is Tran Phu Secondary School. It has 28 classrooms for 28 classes . Each classroom is very large and comfortable for student to study. My school also has a library , a computer room , a music room , and so on ....... I really like the library because it has many useful and interesting books. When I have free time , I often go to the library to study or read books. I love my school very much.

Hello , everyone. My name is Nhi.Today , I will introduce you my topic is " What do you do to keep school clean - green and tidy ? "

What do you do to keep school clean and tidy ? Do you want your school green and clean. What do you think if you study in a messy and dirty school ? For me , I have some following ways to keep school clean. Firstly , when you see trash in a yard , you must pick them up and put in the waste basket. You should plant a lot of trees and  take care of the flowers.

That is my thoughts about " What do you do to keep school clean - green - and tidy ? "

The name of my school is Oxford English School. It is situated in the middle of the town I live in. it is a very large school.

The school building is old but beautiful. There are many classrooms in it. The Principal is a middle-aged European. He is a kind and very efficient man.

The teachers of my school are of many races. Some are Chinese, some are Malay and some are Indian. There are also a few European teachers. They are all very clever and hardworking teachers. All the pupils like them very much.

As there are many pupils in my school, the library, the play ground and the hall are all very large. Pupils may be seen learning in the library, playing in the playground or performing gymnastics in the hall with great interest.

tham khảo thôi nhé bạn

Homeland, the source of this culture native. Homeland is where we were born and grew up, where our forefathers thousands of years to protect and preserve native traditions toc.Homeland is what dear closeness and kinship in everyday life ... is the old story she often told, are my lullaby early days, are hoes, bamboo pallet, baskets or father ... Homeland incense is where we, the survivors signaling his father on holidays, by the simple tray in memory of people who do not khuat.Homeland modern flavor and urban civilization, but it is thought the source was probably live, is the nation's cultural identity which we should inherit and develop.

bạn lưu ý là \(CO_3\) hoá trị II nhé, ko phải I

gọi hoá trị của Ca là \(x\)

\(\rightarrow Ca_1^x\left(CO_3\right)^{II}_1\rightarrow x.1=II.1\rightarrow x=II\)

vậy Ca hoá trị II

Có \(cos^2\alpha=1-sin^2\alpha=\dfrac{16}{25}\)

\(A=5sin^2\alpha+6cos^2\alpha=5\left(sin^2\alpha+cos^2\alpha\right)+cos^2\alpha=5+\dfrac{16}{25}=\dfrac{141}{25}\)