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\(-\left|\dfrac{1}{2}x-2\right|+\dfrac{-2}{3}=\dfrac{-6}{5}\\ \Rightarrow-\left|\dfrac{1}{2}x-2\right|=\dfrac{-6}{5}+\dfrac{2}{3}\\ \Rightarrow-\left|\dfrac{1}{2}x-2\right|=-\dfrac{8}{15}\\ \Rightarrow\left|\dfrac{1}{2}x-2\right|=\dfrac{8}{15}\\ \Rightarrow\left[{}\begin{matrix}\dfrac{1}{2}x-2=\dfrac{8}{15}\\\dfrac{1}{2}x-2=-\dfrac{8}{15}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}\dfrac{1}{2}x=\dfrac{38}{15}\\\dfrac{1}{2}x=\dfrac{22}{15}\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=\dfrac{76}{15}\\x=\dfrac{44}{15}\end{matrix}\right.\)
#$\mathtt{Toru}$
\(-\left|\dfrac{1}{2}x-2\right|+\left(-\dfrac{2}{3}\right)=-\dfrac{6}{5}\\ =>-\left|\dfrac{1}{2}x-2\right|=-\dfrac{6}{5}+\dfrac{2}{3}\\ =>-\left|\dfrac{1}{2}x-2\right|=-\dfrac{8}{15}\\ =>\left|\dfrac{1}{2}x-2\right|=\dfrac{8}{15}\)
TH1: \(\dfrac{1}{2}x-2=\dfrac{8}{15}\left(x\ge4\right)\)
\(\Rightarrow\dfrac{1}{2}x=\dfrac{8}{15}+2=\dfrac{38}{15}\\ \Rightarrow x=\dfrac{38}{15}\cdot2=\dfrac{76}{15}\left(tm\right)\)
TH2: \(\dfrac{1}{2}x-2=-\dfrac{8}{15}\left(x< 4\right)\)
\(\Rightarrow\dfrac{1}{2}x=-\dfrac{8}{15}+2=\dfrac{22}{15}\\ \Rightarrow x=\dfrac{22}{15}\cdot2=\dfrac{44}{15}\left(tm\right)\)
1) D
2) D
3)C
4) D
5) C
6) C
7) D
8) B
Bài này dễ mà bn,chúc bn học tốt ^^
Tom always _____ breakfast before going to work. A. have B. is having C. had D. has
My English teacher _____ Mr Tuan Anh. A. are B. have been C. were D. is
Our lesson _____ at 7.30 a.m every morning. A. begin B. beginning C. begins D. began
I think Mary ____ a job. A. have B. will has C. had D. will have
Chelsea _____ next Sunday. A. wins B. will won C. will win D. won
. Do you like ________? – No, I don’t. A. going camping B. go camping C. to go camping D. go to camping
I am very fond of _______. A. cook B. cooks C. cooking D. to cook
I hope everything _____ fine. A. will B. won’t are C. won’t D. will be
After breakfast, I and my friend ____ to the park every Sunday. A. goes B. go C. is going D. went
Chữ số 6 có giá trị là 60
=>6 là chữ số hàng chục
5 không nằm ở hàng đơn vị
mà 5 không là chữ số hàng chục
nên 5 là chữ số hàng trăm
=>Chữ số hàng đơn vị là 7
Vậy: Số cần tìm là 567
a) Để x là số hữu tỉ dương thì:
\(\dfrac{13-n}{-5}>0\)
Mà: `-5<0`
`=>13-n<0`
`=>n>13`
b) Để x là số hữu tỉ âm thì:
`(13-n)/-5<0`
Mà: `-5<0`
`=>13-n>0`
`=> n<13`
c) Đê x không phải số hữu tỉ âm cũng không phải số hữu tỉ dương thì:
\(x=0=>\dfrac{13-n}{-5}=0\\ =>13-n=0\\ =>n=13\)
Bài 2:
Để \(\dfrac{m+2}{5};\dfrac{m-5}{-6}\) đều là các số dương thì
\(\left\{{}\begin{matrix}\dfrac{m+2}{5}>0\\\dfrac{m-5}{-6}>0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}m+2>0\\m-5< 0\end{matrix}\right.\)
=>-2<m<5
mà m nguyên
nên \(m\in\left\{-1;0;1;2;3;4\right\}\)
Bài 3:
Để \(\dfrac{1-m}{-13};\dfrac{5-m}{3}\) đều là các số âm thì
\(\left\{{}\begin{matrix}\dfrac{1-m}{-13}< 0\\\dfrac{5-m}{3}< 0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{m-1}{13}< 0\\\dfrac{m-5}{3}>0\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}m-1< 0\\m-5>0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}m< 1\\m>5\end{matrix}\right.\)
=>\(m\in\varnothing\)
a: \(-\dfrac{25}{20}< 0;0< \dfrac{20}{25}\)
Do đó: \(-\dfrac{20}{25}< \dfrac{20}{25}\)
b: \(\dfrac{15}{21}=\dfrac{15:3}{21:3}=\dfrac{5}{7};\dfrac{21}{49}=\dfrac{21:7}{49:7}=\dfrac{3}{7}\)
mà 5>3
nên \(\dfrac{15}{21}>\dfrac{21}{49}\)
c: \(\dfrac{-19}{49}=\dfrac{-19\cdot47}{49\cdot47}=\dfrac{-893}{49\cdot47}\)
\(\dfrac{-23}{47}=\dfrac{-23\cdot49}{47\cdot49}=\dfrac{-1127}{47\cdot49}\)
mà -893>-1127
nên \(-\dfrac{19}{49}>-\dfrac{23}{47}\)
\(A=\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{\left(n-1\right)n}\\ =1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{n-1}-\dfrac{1}{n}\\ =1-\dfrac{1}{n}\\ =\dfrac{n-1}{n}\)
\(B=\dfrac{49}{2\cdot9}+\dfrac{49}{9\cdot16}+\dfrac{49}{16\cdot23}+...+\dfrac{49}{65\cdot72}\\ =7\cdot\left(\dfrac{7}{2\cdot9}+\dfrac{7}{9\cdot16}+\dfrac{7}{16\cdot23}+...+\dfrac{7}{65\cdot72}\right)\\ =7\cdot\left(\dfrac{1}{2}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{23}+...+\dfrac{1}{65}-\dfrac{1}{72}\right)\\ =7\cdot\left(\dfrac{1}{2}-\dfrac{1}{72}\right)\\ =7\cdot\dfrac{35}{72}\\ =\dfrac{245}{72}\)
\(E=\dfrac{4}{3\cdot7}+\dfrac{4}{7\cdot11}+...+\dfrac{4}{95\cdot99}\)
\(=\dfrac{1}{3}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{11}+...+\dfrac{1}{95}-\dfrac{1}{99}\)
\(=\dfrac{1}{3}-\dfrac{1}{99}=\dfrac{33}{99}-\dfrac{1}{99}=\dfrac{32}{99}\)
\(D=\dfrac{1}{7}+\dfrac{1}{91}+\dfrac{1}{247}+\dfrac{1}{475}+\dfrac{1}{775}+\dfrac{1}{1147}\)
\(=\dfrac{1}{1\cdot7}+\dfrac{1}{7\cdot13}+\dfrac{1}{13\cdot19}+\dfrac{1}{19\cdot25}+\dfrac{1}{25\cdot31}+\dfrac{1}{31\cdot37}\)
\(=\dfrac{1}{6}\left(\dfrac{6}{1\cdot7}+\dfrac{6}{7\cdot13}+...+\dfrac{6}{31\cdot37}\right)\)
\(=\dfrac{1}{6}\left(1-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{13}+...+\dfrac{1}{31}-\dfrac{1}{37}\right)\)
\(=\dfrac{1}{6}\left(1-\dfrac{1}{37}\right)=\dfrac{1}{6}\cdot\dfrac{36}{37}=\dfrac{6}{37}\)
\(C=\dfrac{3}{1\cdot3}+\dfrac{3}{3\cdot5}+...+\dfrac{3}{49\cdot51}\)
\(=\dfrac{3}{2}\left(\dfrac{2}{1\cdot3}+\dfrac{2}{3\cdot5}+...+\dfrac{2}{49\cdot51}\right)\)
\(=\dfrac{3}{2}\left(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+...+\dfrac{1}{49}-\dfrac{1}{51}\right)\)
\(=\dfrac{3}{2}\left(1-\dfrac{1}{51}\right)=\dfrac{3}{2}\cdot\dfrac{50}{51}=\dfrac{1}{17}\cdot25=\dfrac{25}{17}\)
1. A. prefer B. better C. teacher D. worker
2. A. bear B. hear C. dear D. near
3. A. collect B. concern C. concert D. combine
Circle the odd one out. ( 2 points)
4. A. watches B. brushes C. teacher D. goes
5. A. meat B. fish C. beef D. tea
Toán ạ
Bài 2: Viết các tích sau dưới dạng luỹ thừa, của một số tự nhiên.
a; a4.a6 = a4+6 = a10
b; (a5)7 = a5+7 = a12
c; (a3)4.a9 = a12.a9 = a12+9 = a21
d; (23)5.(23)4 = 215.212 = 215+12 = 227