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5\(\dfrac{8}{17}\):x + (-\(\dfrac{1}{17}\)) : x + 3\(\dfrac{1}{17}\) : 17\(\dfrac{1}{3}\)= \(\dfrac{4}{17}\)
\(\dfrac{93}{17}\).\(\dfrac{1}{x}\) + (-\(\dfrac{1}{17}\)) .\(\dfrac{1}{x}\) +\(\dfrac{3}{17}\)= \(\dfrac{4}{17}\)
\(\dfrac{1}{x}\).\(\dfrac{92}{17}\)=\(\dfrac{1}{17}\)
\(\dfrac{1}{1.4}\)+\(\dfrac{1}{4.7}\)+\(\dfrac{1}{7.10}\)+...+\(\dfrac{1}{x.\left(x+3\right)}\)=\(\dfrac{6}{19}\)
\(a,\frac{20132013}{20142014}=\frac{2013.10001}{2014.10001}=\frac{2013}{2014}=1-\frac{1}{2014};\frac{131313}{141414}=\frac{13.10101}{14.10101}=\frac{13}{14}=1-\frac{1}{14}.\text{Vì: 14 bé hơn 2014 nên:}\frac{1}{14}>\frac{1}{2014}\Rightarrow\frac{20132013}{20142014}>\frac{131313}{141414}\)
\(C=2013^9+2013^9.2013=2013^9\left(2013+1\right)=2013^9.2014;D=2014^9.2014\text{ vì: 2013^9< 2014^9 nên: C bé thua D }\)
\(c,M=\frac{-7}{10^{2005}}+\frac{-15}{10^{2006}}=\frac{-7}{10^{2005}}+\frac{-7}{10^{2006}}+\frac{-8}{10^{2006}};N=\frac{-7}{10^{2005}}+\frac{-7}{10^{2006}}+\frac{-8}{10^{2005}}.Vì:10^{2006}>10^{2005}.Nên:\frac{-8}{10^{2006}}>\frac{-8}{10^{2005}}\Rightarrow M>N\)
Thế bạn có làm được không Võ Nguyễn Anh Thư? Trả lời thì trả lời câu hỏi ý, trả lời cái đấy để làm gì?
Ace Legona, Hoàng Thị Ngọc Anh, ... giúp mình câu này với!
A= 1+2-3-4+5+6-7-8+...+2013+2014
A=(1+2-3-4)+(5+6-7-8)+.....+(2013+2014)
A=(-4)+(-4)+...+(-4)+4027
A=(-4).503+4027
A=-2012+4027
A=2015
B=\(\dfrac{3}{2}\cdot\dfrac{4}{3}\cdot...\cdot\dfrac{2016}{2015}\)
B=\(\dfrac{3.4.5.6.....2016}{2.3.4.5.....2015}=\dfrac{2016}{2}=1008\)
Mấy bài dễ u tự giải quyết nha
3) \(\dfrac{2013}{2014}+\dfrac{2014}{2015}+\dfrac{2015}{2013}\)
\(=\left(1-\dfrac{1}{2014}\right)+\left(1-\dfrac{1}{2015}\right)+\left(1+\dfrac{2}{2013}\right)\)
\(=3+\dfrac{2}{2013}-\dfrac{1}{2014}-\dfrac{1}{2015}\)
\(=3+\left(\dfrac{1}{2013}-\dfrac{1}{2014}\right)+\left(\dfrac{1}{2013}-\dfrac{1}{2015}\right)>3\)
a) Giải
Ta có: \(S=\dfrac{1}{2}+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{2012}}+\dfrac{1}{2^{2013}}\)
\(\Rightarrow2S=\dfrac{2}{2}+\dfrac{2}{2^2}+\dfrac{2}{2^3}+...+\dfrac{2}{2^{2012}}+\dfrac{2}{2^{2013}}\)
\(2S=1+\dfrac{1}{2}+\dfrac{1}{2^2}+...+\dfrac{1}{2^{2011}}+\dfrac{1}{2^{2012}}\)
\(\Rightarrow2S-S=1+\dfrac{1}{2}+\dfrac{1}{2^2}+...+\dfrac{1}{2^{2011}}+\dfrac{1}{2^{2012}}-\dfrac{1}{2}-\dfrac{1}{2^2}-\dfrac{1}{2^3}-...-\dfrac{1}{2^{2012}}-\dfrac{1}{2^{2013}}\)
\(\Rightarrow S=1-\dfrac{1}{2^{2013}}\)
\(\Rightarrow S=\dfrac{2^{2013}-1}{2^{2013}}\)
b) Giải
Từ \(A=\dfrac{2011^{2012}+1}{2011^{2013}+1}\)
\(\Rightarrow2011A=\dfrac{2011^{2013}+20111}{2011^{2013}+1}=\dfrac{2011^{2013}+1+2010}{2011^{2013}+1}=1+\dfrac{2010}{2011^{2013}+1}\)
Từ \(B=\dfrac{2011^{2013}+1}{2011^{2014}+1}\)
\(\Rightarrow2011B=\dfrac{2011^{2014}+2011}{2011^{2014}+1}=\dfrac{2011^{2014}+1+2010}{2011^{2014}+1}=1+\dfrac{2010}{2011^{2014}+1}\)
Vì 20112013 + 1 < 20112014 + 1 và 2010 > 0
\(\Rightarrow\dfrac{2010}{2011^{2013}+1}>\dfrac{2010}{2011^{2014}+1}\)
\(\Rightarrow2011A>2011B\)
\(\Rightarrow A>B\)
Vậy A > B.
Ta có:
\(A=\dfrac{9}{a^{2013}}+\dfrac{7}{a^{2014}}\)
\(=\left(\dfrac{8}{a^{2013}}+\dfrac{1}{a^{2013}}\right)+\left(\dfrac{8}{a^{2014}}-\dfrac{1}{a^{2014}}\right)\)
\(=\left(\dfrac{8}{a^{2013}}+\dfrac{8}{a^{2014}}\right)+\left(\dfrac{1}{a^{2013}}-\dfrac{1}{a^{2014}}\right)\)
\(B=\dfrac{8}{a^{2014}}+\dfrac{8}{a^{2013}}\)
\(=\dfrac{8}{a^{2013}}+\dfrac{8}{a^{2014}}\)
Vì \(\dfrac{1}{a^{2013}}>\dfrac{1}{a^{2014}}\Rightarrow\dfrac{1}{a^{2013}}-\dfrac{1}{a^{2014}}>0\)
\(\Rightarrow\left(\dfrac{8}{a^{2013}}+\dfrac{8}{a^{2014}}\right)+\left(\dfrac{1}{a^{2013}}-\dfrac{1}{a^{2014}}\right)>\dfrac{8}{a^{2013}}+\dfrac{8}{a^{2014}}\)
Vậy \(A>B\)
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