\(3,\\ a,\dfrac{2011}{2010}=1+\dfrac{1}{2010};\dfrac{3011}{3010}=1+\dfrac{1}{3010}\\ \dfrac{1}{2010}>\dfrac{1}{3010}\left(2010< 3010\right)\Rightarrow\dfrac{2011}{2010}>\dfrac{3011}{3010}\\ b,A=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{99}-\dfrac{1}{100}\\ A=\left(1+\dfrac{1}{3}+...+\dfrac{1}{99}\right)-\left(\dfrac{1}{2}+\dfrac{1}{4}+...+\dfrac{1}{100}\right)\\ A=\left(1+\dfrac{1}{3}+...+\dfrac{1}{99}\right)+\left(\dfrac{1}{2}+\dfrac{1}{4}+...+\dfrac{1}{100}\right)-2\left(\dfrac{1}{2}+\dfrac{1}{4}+...+\dfrac{1}{100}\right)\\ A=\left(1+\dfrac{1}{2}+\dfrac{1}{3}+...+\dfrac{1}{100}\right)-\left(1+\dfrac{1}{2}+...+\dfrac{1}{50}\right)\\ A=\dfrac{1}{51}+\dfrac{1}{52}+....+\dfrac{1}{100}=B\)

\(4,\\ a,\dfrac{x+5}{x+1}=1+\dfrac{4}{x+1}\in Z\Leftrightarrow4⋮x+1\\ \Leftrightarrow x+1\inƯ\left(4\right)=\left\{-4;-2;-1;1;2;4\right\}\\ \Leftrightarrow x\in\left\{-5;-3;-2;0;1;3\right\}\\ b,\dfrac{2x+4}{x+3}=\dfrac{2\left(x+3\right)-2}{x+3}=2-\dfrac{2}{x+3}\in Z\\ \Leftrightarrow2⋮x+3\Leftrightarrow x+3\inƯ\left(2\right)=\left\{-2;-1;1;2\right\}\\ \Leftrightarrow x\in\left\{-5;-4;-2;-1\right\}\)

\(5,\\ -\left|3x+\dfrac{1}{5}\right|\le0\\ \Leftrightarrow A=2017-\left|3x+\dfrac{1}{5}\right|\le2017\\ A_{max}=2017\Leftrightarrow3x+\dfrac{1}{5}=0\Leftrightarrow x=-\dfrac{1}{15}\\ 6,\\ \left\{{}\begin{matrix}\left(x+\dfrac{1}{2}\right)^2\ge0\\\left|2y-\dfrac{3}{4}\right|\ge0\end{matrix}\right.\Leftrightarrow A=\left(x+\dfrac{1}{2}\right)^2+\left|2y-\dfrac{3}{4}\right|+\dfrac{175}{3}\ge\dfrac{175}{3}\\ A_{min}=\dfrac{175}{3}\Leftrightarrow\left\{{}\begin{matrix}x+\dfrac{1}{2}=0\\2y-\dfrac{3}{4}=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-\dfrac{1}{2}\\y=\dfrac{3}{8}\end{matrix}\right.\)

Bài 5: 

\(A=-\left|3x+\dfrac{1}{5}\right|+2017\le2017\forall x\)

Dấu '=' xảy ra khi \(x=-\dfrac{1}{15}\)

\(7⋮\left(2n-3\right)\Leftrightarrow2n-3\inƯ\left(7\right)=\left\{-7,-1,1,7\right\}\)

\(\Leftrightarrow2n\in\left\{-4,2,4,10\right\}\Leftrightarrow n\in\left\{-2,1,2,5\right\}\).

Hành vi của Lan là sai .Vì bao che cho hành vi sai của bạn nếu bn chx làm thì sẽ nhắc nhở bạn

Hành vi của Lan là thiếu trung thực trái với phẩm chất chí công vô tư . 

1.

\(Ca+2H_2O\rightarrow Ca\left(OH\right)_2+H_2\)

\(2Na+2H_2O\rightarrow2NaOH+H_2\)

\(P_2O_5+3H_2O\rightarrow2H_3PO_4\)

\(K_2O+H_2O\rightarrow2KOH\)

\(SO_2+H_2O\rightarrow H_2SO_3\)

\(SO_3+H_2O\rightarrow H_2SO_4\)

2.

(1)\(2KMnO_4\rightarrow\left(t^o\right)K_2MnO_4+MnO_2+O_2\)

(2)\(2Cu+O_2\rightarrow\left(t^o\right)2CuO\)

(3)\(CuO+H_2\rightarrow\left(t^o\right)Cu+H_2O\)

(4)\(4Na+O_2\rightarrow\left(t^o\right)2Na_2O\)

(5)\(Na_2O+H_2O\rightarrow2NaOH\)

(6)\(S+O_2\rightarrow\left(t^o\right)SO_2\)

(7)\(SO_2+H_2O\rightarrow H_2SO_3\)

(1) 2KMnO₄ --to--> K₂MnO₄ + MnO₂ + O₂

(2) 2Cu + O₂ --to--> 2CuO

(3) CuO + CO --to--> Cu + CO₂

(4) 4Na + O₂ --to--> 2Na₂O

(5) Na₂O + H₂O ---> 2NaOH

(6) S + O₂ --to--> SO₂

(7) SO₂ + H₂O ---> H₂SO₃

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