đề thi năm 2012-2013 tỉnh thái bình
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NV
3
1 tháng 2 2017
01. An's hobby is collecting stamps.
02. My brother has a bad habit: watching TV while eating
03. It's good to donate blood because you can save people's life.
04. My mum loves buying flowers and put them in different vases.
05. My favorite food is omelette
1 tháng 2 2017
Fill in each blank with a suitable word. The first letter of the word has been provided:
01. An's hobby is collecting..........................stamps.
02. My brother has a bad habit: watching.......................... TV while eating
03. It's good to donate.......................blood because you can save people's life.
04. My mum loves buying flowers.........................and put them in different vases.
05. My favorite food is omelet...............................
S
13 tháng 9 2017
\(S=1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{2011}-\frac{1}{2012}+\frac{1}{2013}\)
\(=\left(1+\frac{1}{3}+...+\frac{1}{2011}+\frac{1}{2013}\right)-\left(\frac{1}{2}+\frac{1}{4}+...+\frac{1}{2012}\right)\)
\(=1+\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2012}+\frac{1}{2013}-2\left(\frac{1}{2}+\frac{1}{4}+...+\frac{1}{2012}\right)\)
\(=1+\frac{1}{2}+...+\frac{1}{2012}+\frac{1}{2013}-\left(1+\frac{1}{2}+...+\frac{1}{1006}\right)\)
\(=\frac{1}{1007}+\frac{1}{1008}+...+\frac{1}{2012}+\frac{1}{2013}\)
=> S = P => (S - P)2013 = 0
TN
13 tháng 9 2017
\(S=1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+\frac{1}{5}-\frac{1}{6}+...+\frac{1}{2011}-\frac{1}{2012}+\frac{1}{2013}\)
\(\Rightarrow S=1+\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2013}-2\left(\frac{1}{2}+\frac{1}{4}+...+\frac{1}{2012}\right)\)
\(\Rightarrow S=1+\frac{1}{2}+\frac{1}{3}+...+\frac{1}{2013}-1-\frac{1}{2}-\frac{1}{3}-...-\frac{1}{1006}\)
\(\Rightarrow S=\frac{1}{1007}+\frac{1}{1008}+...+\frac{1}{2012}+\frac{1}{2013}\)\(=P\)
\(\Rightarrow\left(S-P\right)^{2013}=0^{2013}=0\)
Tík cho mik nha!
WA
2
25 tháng 10 2018
Link đây :
https://dethi.violet.vn/present/show/entry_id/4263264
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KO CÓ J