Cảm nghĩ về bài thơ "Tiếng gà trưa" của Xuân Quỳnh.

Ta có : \(1+2+\) \(2^2+2^3+2^4+...+2^{2009}+2^{2010}\)

\(\Rightarrow2B=2+2^2+2^3+...+2^{2010}+2^{2011}\)

\(\Rightarrow2B-B=B=2^{2011}-1\)

Vậy \(B=2^{2011}-1\)

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1-d

2-b

3-a

4-c

1.We need more calories or energy to do somethings everyday.

2.Eat less sweet food and eat more fruit or vegetables.

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1.A

2.đề sai

Hãy viết một vài thuyết trình về phồng ngủ của em.

Ta có:

\(\frac{a}{b}=\frac{a\left(b+2017\right)}{b\left(b+2017\right)}=\frac{ab+a2017}{b\left(b+2017\right)}\left(1\right)\)

\(\frac{a+2017}{b+2017}=\frac{b\left(a+2017\right)}{b\left(b+2017\right)}=\frac{ab+b2017}{b\left(b+2017\right)}\left(2\right)\)

Từ (1) và (2), suy ra:

_Nếu a>b thì \(\frac{ab+a2017}{b\left(b+2017\right)}>\frac{ba+b2017}{b\left(b+2017\right)}\Leftrightarrow\frac{a}{b}>\frac{a+2017}{b+2017}\)

_Nếu a<b thì\(\frac{ab+a2017}{b\left(b+2017\right)}< \frac{ba+b2017}{b\left(b+2017\right)}\Leftrightarrow\frac{a}{b}< \frac{a+2017}{b+2017}\)

_Nếu a=b thì\(\frac{ab+a2017}{b\left(b+2017\right)}=\frac{ba+b2017}{b\left(b+2017\right)}\Leftrightarrow\frac{a}{b}=\frac{a+2017}{b+2017}\)