\(C=4+4^2+4^3+...+4^{2021}+4^{2022}\)

\(=\left(4+4^2\right)+\left(4^3+4^4\right)+...+\left(4^{2021}+4^{2022}\right)\)

\(=4.\left(1+4\right)+4^3.\left(1+4\right)+...+4^{2021}.\left(1+4\right)\)

\(=4.5+4^3.5+...+4^{2021}.5\)

\(=5.\left(4+4^3+...+4^{2021}\right)⋮5\)

Vậy \(C⋮5\)

1 A

2 A

Part B: Find the word whose stress is pronounced differently from others.

\(25\times36,145\times4=36,145\times100\)

Số cần điền vào chỗ chấm là 4.

\(25\times36,145\times4=36,145\times100\)

Số cần điền là 4

1. B

2. C

Part A: Find the word whose underlined part is pronounced differently from others.

Bài 1

\(\left(1-\dfrac{1}{99}\right)\times\left(1-\dfrac{1}{100}\right)\times...\times\left(1-\dfrac{1}{2006}\right)\)

\(=\dfrac{98}{99}\times\dfrac{99}{100}\times...\times\dfrac{2005}{2006}\)

\(=\dfrac{98}{2006}\)

\(=\dfrac{49}{1003}\)

Bài 2

\(\dfrac{111}{333}=\dfrac{111:111}{333:111}=\dfrac{1}{3}\)

\(\dfrac{2222}{4444}=\dfrac{2222:2222}{4444:2222}=\dfrac{1}{2}\)

Do \(3>2\Rightarrow\dfrac{1}{3}< \dfrac{1}{2}\)

Vậy \(\dfrac{111}{333}< \dfrac{2222}{4444}\)

Bài 1.

\(\left(1-\dfrac{1}{99}\right)\times\left(1-\dfrac{1}{100}\right)\times...\times\left(1-\dfrac{1}{2006}\right)\)

\(=\dfrac{98}{99}\times\dfrac{99}{100}\times...\times\dfrac{2005}{2006}\)

\(=\dfrac{98\times99\times...\times2005}{99\times100\times...2006}\)

\(=\dfrac{98}{2006}\)

\(=\dfrac{49}{1003}\)

Bài 2.

Có: \(\dfrac{111}{333}=\dfrac{111}{3\times111}=\dfrac{1}{3}\)

\(\dfrac{2222}{4444}=\dfrac{2222}{2\times2222}=\dfrac{1}{2}\)

Vì \(\dfrac{1}{3}< \dfrac{1}{2}\) nên \(\dfrac{111}{333}< \dfrac{2222}{4444}\)

Ta có:

9,708 < 9,718 < 9,728 < 9,738 < 9,748 < 9,758

\(\Rightarrow x=0;x=1;x=2;x=3;x=4\)

9,7x8 < 9,758 

Các số thỏa mãn là: 9,708; 9,718; 9,728; 9,738; 9,748 

Các số x thỏa mãn là: 0; 1; 2; 3; 4 

1)

\(5⋮\left(n+2\right)\)

\(\Rightarrow n+2\inƯ\left(5\right)=\left\{-5;-1;1;5\right\}\)

\(\Rightarrow n\in\left\{-7;-3;-1;3\right\}\)

2) 

Ta có:

\(n+7=n+1+6\)

Để \(\left(n+7\right)⋮\left(n+1\right)\) thì \(6⋮\left(n+1\right)\)

\(\Rightarrow n+1\inƯ\left(6\right)=\left\{-6;-3;-2;-1;1;2;3;6\right\}\)

\(\Rightarrow n\in\left\{-7;-4;-3;-2;0;1;2;5\right\}\)

tham khảo câu 1 nha 
 

A = 4 ( 2 sinx . cosx )² . cos²2x + cos²4x

A = 4 . sin²2x . cos²2x + cos²4x

A = ( 2 sin2x . cos2x)² + cos²4x

A = sin² 4x + cos²4x  = 1