Số đoạn tạo thành : 1+2+3+...+(n-3)+(n-2)+(n-1)

Nghề điện dân dụng luôn cần phát triển để phục vụ sự nghiệp công nghiệp hóa và hiện đại hóa đất nước.

- Tương lai nghề điện dân dụng gắn liền với sự phát triển điện năng, đồ dùng điện và tốc độ phát triển xây dựng nhà ở.

- Nghề điện dân dụng có nhiều điều kiện phát triển không những ở thành phố mà còn ở nông thôn, miền núi.

- Do sự phát triển của cách mạng khoa học và kĩ thuật, luôn xuất hiện nhiều thiết bị mới có nhiều tính năng hiện đại đòi hỏi người thợ điện luôn phải cập nhật, nâng cao kiến thức và kĩ năng nghề nghiệp.

\(A=\left(3^8.17+3^9.5\right):3^7.25\)

\(A=\left[3^8.\left(17+5\right).3\right]:3^7.25\)

\(A=\left(3^8.22.3\right):3^7.25\)

\(A=3^9.22:3^7.25\Leftrightarrow A=\left(3^9:3^7\right).22.25\)

\(A=3^2.22.25\Leftrightarrow A=9.22.25\Leftrightarrow A=198.25\)

\(A=4950\)

a) \(-5x+\frac{1}{2}=\frac{2}{3}\\ -5x=\frac{2}{3}-\frac{1}{2}\\ -5x=\frac{1}{6}\\ x=\frac{1}{6}:\left(-5\right)\\ x=\frac{-1}{30}\)Vậy \(x=\frac{-1}{30}\)

b) \(\frac{1}{-5}-\frac{2}{3}+1\frac{1}{2}x=\frac{1}{2}\\ \frac{-13}{15}+\frac{3}{2}x=\frac{1}{2}\\ \frac{3}{2}x=\frac{1}{2}-\frac{-13}{15}\\ \frac{3}{2}x=\frac{41}{30}\\ x=\frac{41}{30}:\frac{3}{2}\\ x=\frac{41}{45}\)Vậy \(x=\frac{41}{45}\)

c) \(2\left(\frac{1}{4}-3x\right)=\frac{1}{5}-4x\\ \frac{1}{2}-6x=\frac{1}{5}-4x\\ \frac{1}{2}-\frac{1}{5}=6x-4x\\ \frac{3}{10}=2x\\ x=\frac{3}{10}:2\\ x=\frac{3}{20}\)Vậy \(x=\frac{3}{20}\)

d) \(\frac{-5}{2}-3\left(\frac{1}{3}-x\right)=\frac{1}{4}-7x\\ \frac{-5}{2}-1+3x=\frac{1}{4}-7x\\ \frac{-7}{2}+3x=\frac{1}{4}-7x\\ 7x+3x=\frac{1}{4}+\frac{7}{2}\\ 10x=\frac{15}{4}\\ x=\frac{15}{4}:10\\ x=\frac{3}{8}\)Vậy \(x=\frac{3}{8}\)

\(-5x+\frac{1}{2}=\frac{2}{3}\)

⇔\(\frac{-5x.6}{6}+\frac{3}{6}=\frac{4}{6}\)

➞\(30x+3=4\)

⇔\(30x=1\)

⇔\(x=\frac{1}{30}\)

2Mx0y+2yH2S04=>xM2(S04)2y/x+2yH20
Gọi a là số mol của Mx0y:
_m(xM2(S04)2y/x)=a(Mx+96y) (g)
_mddsaupư=a(2Mx+16y)+98a*100%/24.5%
=a(2Mx+416y) (g)
Ta có phương trình:
a(Mx+96y)/a(Mx+416y)=32.2%/100%=0.322
<=>Mx+96y=0.322Mx+133.952y
<=>0.678Mx=37.952y
<=>M=28y/x
Đặt 2y/x=n
=>M=28n
_n=1=>M=28(loại)
_n=2=>M=56(nhận)
_n=3=>M=84(loại)
Vậy M là sắt(Fe)
Ta có:n=2=>2y=2x
<=>x=y
Ta chọn công thức đơn giản nhất với x:y =1:1
Vậy công thức oxit là FeO.

Chúc bạn học tốt nha LIÊN

1. ĐK: x>3\(\sqrt{x-2+2\sqrt{x-3}}=\sqrt{\left(x-3\right)+2\sqrt{x-3}+1}=\sqrt{\left(\sqrt{x-3}+1\right)^2}=\sqrt{x-3}+1\\ \)2( Tương tự) Bớt 1 thêm 1

Chien and I stuied in the same secondary class. He was a little overwieght and not quite tall, however, his outlook with bright complexion and crew hair was appealing. frankly, at first he hadn’t left any impression on me, but, once we were set to sit together, i found him a interesting and jovial person.Moreover, he was very active, it appeared that if he didn’t take part in the class activity, the things wouldn’t have run smoothly. Yet, Chien’s studying was not good, therefore, wherever he asked me anything about the lesson, i awlays tried my best to explain it to him. On the other hand, thanks to Chien, i learnt many fascinating games, or good amusement places after the class. what a pity that we no longer studied in the same school. My family moved to another city, we scacrely meeteach other. however, we still keep in touch and we are always best friend.

Among my friends, I cherish the most is Ha.She is a good student of my class, she lived with her parents in a small house near my house. She has long black hair, oval face and eyes speak. What particularly struck me about her was the smile. She looks so cute when he smiles. She is a form of friends that I can share everything. She always believed and helped me in every situation. She is friendly, gentle and endearing all friends. She likes Literacy, reading, listening to music and go under heaven mua.Chung I have a lot in common with each other, has become good friends over the past 5 years. Although time has passed long in any case, I'm and Ha also trying to keep this friendship

I have a best friend ever in my life named Ashutosh. He is someone special in my life who helps me in my every difficulty. He is someone who showed me right path. He always has time for me even in his busy schedule. He is my neighbour that’s why we become together even after school time. We go together at picnic whenever we get vacation from school. We enjoy our festival holidays together and with each other’s family. We go to see Ramlila fair in the Ramlila ground together and enjoy a lot. We always take part in every extracurricular activities of the school. We love to play cricket and carom at home. He is more than a mentor for me because he always gives me right decisions whenever I become in difficulty.

He is so special for me in my life; I never do anything without him. He always become in a good mood and never compromise with wrong ways. He always does right things and motivates every one of us in the classroom to do the same. He always has smiling face even in his difficult times and never let his difficulties to come on his face. He is a good counsellor and loves to explain anything. He cares for his parents, grandparents and other family members. He obeys them always and other old people of the society. I met him first time when I was in the fifth grade and now we are in 8th standard in the same section.

He is very tall and looks different from my other classmates. Once I was very upset because of money problem. I could not buy all necessary books in the class 6. He asked me, what happened and I told him my story. He said that, for this small problem you are so worry and not happy for some days. He laughed and told me that don’t worry we can share all books in the school as well as at home. You don’t need to buy even any single book for whole year. After that he made me laugh through his jokes and stories. I never forget that moment he helped me and always become ready to help him too. He is so practical and never mixes the personal and professional life. He helps me always whenever I get difficulties in solving my Maths homework. Our likes and dislikes never match however we are best friends.

Among my friends, I cherish the most is Ha.She is a good student of my class, she lived with her parents in a small house near my house. She has long black hair, oval face and eyes speak. What particularly struck me about her was the smile. She looks so cute when he smiles. She is a form of friends that I can share everything. She always believed and helped me in every situation. She is friendly, gentle and endearing all friends. She likes Literacy, reading, listening to music and go under heaven mua.Chung I have a lot in common with each other, has become good friends over the past 5 years. Although time has passed long in any case, I'm and Ha also trying to keep this friendship

Chien and I stuied in the same secondary class. He was a little overwieght and not quite tall, however, his outlook with bright complexion and crew hair was appealing. frankly, at first he hadn’t left any impression on me, but, once we were set to sit together, i found him a interesting and jovial person.Moreover, he was very active, it appeared that if he didn’t take part in the class activity, the things wouldn’t have run smoothly. Yet, Chien’s studying was not good, therefore, wherever he asked me anything about the lesson, i awlays tried my best to explain it to him. On the other hand, thanks to Chien, i learnt many fascinating games, or good amusement places after the class. what a pity that we no longer studied in the same school. My family moved to another city, we scacrely meeteach other. however, we still keep in touch and we are always best friend.

Hi,I'm Thao,i'm a student of class 7a3. I have many best friends in that class.But my close friend is Anh. Her full name is Pham Thi Hoang Anh.She is a good student in my class. Hoang Anh has a round face and long black hair. Her eyes are round and big,color of the eyes are black and brown. Her white skin beautify her natural beauty. She has slender hands, so she always cooks many good food. I am very proud of her, I want to our friendship lasting forever and ever.Thanks for watching !

Sắp xếp các từ sau thành câu có nghĩa:

1.satellite/variety/and/tv/of/ it's/programs/froma/possibla/wide/with/cable/to chose.

With satellite and cable TV, it's possible to choose from a wide variety of programs.

2.artist/young/pop/of/their/ people/latest/favourite/and/ show/like/hear/the/see/to/the/ music.

Young people like to hear the latest pop music and see the show of their favourite artists