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TM
1
DK
25 tháng 10 2021
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.
PA
17 tháng 7 2017
\(\dfrac{1+3\sqrt{2}-2\sqrt{3}}{\sqrt{6}+\sqrt{3}+\sqrt{2}}\)
\(=\dfrac{\left[1+\sqrt{6}\left(\sqrt{3}-\sqrt{2}\right)\right]\left[\sqrt{6}-\left(\sqrt{3}+\sqrt{2}\right)\right]}{\left[\sqrt{6}+\left(\sqrt{3}+\sqrt{2}\right)\right]\left[\sqrt{6}-\left(\sqrt{3}+\sqrt{2}\right)\right]}\)
Tử:
\(\left[1+\sqrt{6}\left(\sqrt{3}-\sqrt{2}\right)\right]\left[\sqrt{6}-\left(\sqrt{3}+\sqrt{2}\right)\right]\)
\(=\sqrt{6}-\left(\sqrt{3}+\sqrt{2}\right)+6\left(\sqrt{3}-\sqrt{2}\right)-\sqrt{6}\) (nhân phân phối)
\(=5\sqrt{3}-7\sqrt{2}\)
Mẫu:
\(\left[\sqrt{6}+\left(\sqrt{3}+\sqrt{2}\right)\right]\left[\sqrt{6}-\left(\sqrt{3}+\sqrt{2}\right)\right]\)
\(=6-\left(5+2\sqrt{6}\right)\)
\(=1-2\sqrt{6}\)
Ta có:
\(\dfrac{5\sqrt{3}-7\sqrt{2}}{1-2\sqrt{6}}\)
\(=\dfrac{\left(5\sqrt{3}-7\sqrt{2}\right)\left(1+2\sqrt{6}\right)}{1-24}\)
\(=\dfrac{5\sqrt{3}+30\sqrt{2}-7\sqrt{2}-28\sqrt{3}}{-23}\)
\(=\dfrac{-23\left(\sqrt{3}-\sqrt{2}\right)}{-23}\)
\(=\sqrt{3}-\sqrt{2}\)
20 tháng 9 2018
\(A=\left(3^8.17+3^9.5\right):3^7.25\)
\(A=\left[3^8.\left(17+5\right).3\right]:3^7.25\)
\(A=\left(3^8.22.3\right):3^7.25\)
\(A=3^9.22:3^7.25\Leftrightarrow A=\left(3^9:3^7\right).22.25\)
\(A=3^2.22.25\Leftrightarrow A=9.22.25\Leftrightarrow A=198.25\)
\(A=4950\)
TD
24 tháng 7 2017
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
DM
3
O
13 tháng 8 2017
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.
26 tháng 9 2017
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
V
5
2 tháng 1 2018
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
2 tháng 1 2018
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.
1 tháng 7 2019
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 \(x=\frac{3}{8}\)
D
21 tháng 3 2018
\(\frac{x}{7}=\frac{x+36}{35}\)
\(\Rightarrow x.35=7.\left(x+36\right)\)
\(\Rightarrow35x=7x+252\)
\(\Rightarrow35x-7x=252\)
\(\Rightarrow28x=252\)
\(\Rightarrow x=9\)
câu 13: 2222
câu 14: thứ tư
câu 15: 88
câu 19:980
câu 20:7
câu 18: 19/10