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NT
1
31 tháng 12 2016
\(\frac{1-x}{2015}+\frac{2-x}{1007}+\frac{3-x}{671}=\frac{1992-x}{4}\)
\(\Rightarrow\frac{1-x}{2015}+1+\frac{2-x}{1007}+2+\frac{3-x}{671}+3=\frac{1992-x}{4}+6\)
\(\Rightarrow\frac{2016-x}{2015}+\frac{2016-x}{1007}+\frac{2016-x}{671}=\frac{2016-x}{4}\)
\(\Rightarrow\frac{2016-x}{2015}+\frac{2016-x}{1007}+\frac{2016-x}{671}-\frac{2016-x}{4}=0\)
\(\Rightarrow\left(2016-x\right)\left(\frac{1}{2015}+\frac{1}{1007}+\frac{1}{671}-\frac{1}{4}\right)=0\)
\(\Rightarrow2016-x=0\).Do \(\frac{1}{2015}+\frac{1}{1007}+\frac{1}{671}-\frac{1}{4}\ne0\)
\(\Rightarrow x=2016\)
LT
15 tháng 3 2020
\(\frac{x+2}{2017}+\frac{x+3}{2016}+\frac{x+4}{2015}+\frac{x+5}{1007}+\frac{x+2074}{11}=0\)
\(\Leftrightarrow\frac{x+2}{2017}+1+\frac{x+3}{2016}+1+\frac{x+4}{2015}+1+\frac{x+5}{1007}+2+\frac{x+2074}{11}-5=0\)
\(\Leftrightarrow\frac{x+2019}{2017}+\frac{x+2019}{2016}+\frac{x+2019}{2015}+\frac{x+2019}{1007}+\frac{x+2019}{11}=0\)
\(\Leftrightarrow\left(x+2019\right)\left(\frac{1}{2017}+\frac{1}{2016}+\frac{1}{2015}+\frac{1}{1007}+\frac{1}{11}\right)=0\)
\(\Leftrightarrow\left(x+2019\right)=0vì\left(\frac{1}{2017}+\frac{1}{2016}+\frac{1}{2015}+\frac{1}{1007}+\frac{1}{11}\right)\ne0\)
\(\Leftrightarrow x=-2019\)
DP
7 tháng 8 2017
Bài 1 :
\(\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+....+\frac{1}{2018}}{\frac{2017}{1}+\frac{2016}{2}+\frac{2015}{3}+...+\frac{1}{2017}}\)
\(=\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2018}}{\left(\frac{2017}{1}+1\right)+\left(\frac{2016}{2}+1\right)+\left(\frac{2015}{3}+1\right)+...+\left(\frac{1}{2017}+1\right)+1}\)
\(=\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2018}}{\frac{2018}{1}+\frac{2018}{2}+\frac{2018}{3}+....+\frac{2018}{2017}+\frac{2018}{2018}}\)
\(=\frac{\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2018}}{2018.\left(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{2017}+\frac{1}{2018}\right)}\)
\(=\frac{1}{2018}\)
8 tháng 8 2017
B=\(\frac{\frac{1}{51}+\frac{1}{53}+...+\frac{1}{149}}{\frac{1}{101.99}+\frac{1}{103.97}+...+\frac{1}{149.51}}\)
\(\)TA CÓ E=\(\frac{1}{101.99}+\frac{1}{103.97}+...+\frac{1}{149.51}\)
\(200E=\frac{200}{101.99}+\frac{200}{103.97}+..+\frac{200}{149.51}\)
\(200E=\frac{101+99}{101.99}+\frac{103+97}{103.97}+...+\frac{149+51}{149.51}\)
\(200E=\frac{1}{99}+\frac{1}{101}+\frac{1}{97}+\frac{1}{103}+...+\frac{1}{51}+\frac{1}{149}\)
\(200E=\frac{1}{51}+\frac{1}{53}+...+\frac{1}{147}+\frac{1}{149}\)
\(E=\left(\frac{1}{51}+\frac{1}{53}+...+\frac{1}{147}+\frac{1}{149}\right):200\)\(=\left(\frac{1}{51}+\frac{1}{53}+...+\frac{1}{147}+\frac{1}{149}\right).\frac{1}{200}\)
\(\Rightarrow B=\frac{1}{51}+\frac{1}{53}+...+\frac{1}{149}\)/\(\left(\frac{1}{51}+\frac{1}{53}+..+\frac{1}{149}\right).\frac{1}{200}\)
\(\Rightarrow B=\frac{1}{\frac{1}{200}}=200\)
VẬY B=200
5 tháng 12 2015
a) (x-5)x+2015 - (x-5)x+2014 =0
(x-5)x+2014(x-5 -1) =0
+ x -5 =0 => x =5
+ x -6 =0 => x =6
Vậy x = 5 hoặc x =6
13 tháng 8 2019
a) \(\frac{x+2015}{5}+\frac{x+2016}{4}=\frac{x+2017}{3}+\frac{x+2018}{2}\)
\(\Leftrightarrow\frac{x+2015}{5}+\frac{5}{5}+\frac{x+2016}{4}+\frac{4}{4}=\frac{x+2017}{3}+\frac{3}{3}+\frac{x+2018}{2}+\frac{2}{2}\)
\(\Leftrightarrow\frac{x+2020}{5}+\frac{x+2020}{4}=\frac{x+2020}{3}+\frac{x+2002}{2}\)
\(\frac{x+2020}{5}+\frac{x+2020}{4}-\frac{x+2020}{3}-\frac{x+2020}{2}=0\)
\(\Leftrightarrow\left(x+2020\right).\left(\frac{1}{5}+\frac{1}{4}-\frac{1}{3}-\frac{1}{2}\right)=0\)
\(\Leftrightarrow x+2020=0\)
\(\Leftrightarrow x=-2020\)
Vậy : \(x=-2020\)
Chúc bạn học tốt !!
13 tháng 8 2019
a) \(\frac{x+2015}{5}+\frac{x+2016}{4}=\frac{x+2017}{3}+\frac{x+2018}{2}\\ \left(\frac{x+2015}{5}+1\right)+\left(\frac{x+2016}{4}+1\right)=\left(\frac{x+2017}{3}+1\right)+\left(\frac{x+2018}{2}+1\right)\\ \frac{x+2020}{5}+\frac{x+2020}{4}=\frac{x+2020}{3}+\frac{x+2020}{2}\\ \frac{x+2020}{5}+\frac{x+2020}{4}-\frac{x+2020}{3}-\frac{x+2020}{2}=0\\ \left(x+2020\right)\left(\frac{1}{5}+\frac{1}{4}-\frac{1}{3}-\frac{1}{2}\right)=0\\ \Rightarrow x+2020=0\\ \Rightarrow x=-2020\)
Vậy x = -2020
b) \(\frac{x+2015}{5}+\frac{x+2016}{6}=\frac{x+2017}{7}+\frac{x+2018}{8}\\ \left(\frac{x+2015}{5}-1\right)+\left(\frac{x+2016}{6}-1\right)=\left(\frac{x+2017}{7}-1\right)+\left(\frac{x+2018}{8}-1\right)\\ \frac{x+2010}{5}+\frac{x+2010}{6}=\frac{x+2010}{7}+\frac{x+2010}{8}\\ \frac{x+2010}{5}+\frac{x+2010}{6}-\frac{x+2010}{7}-\frac{x+2010}{8}=0\\ \left(x+2010\right)\left(\frac{1}{5}+\frac{1}{6}-\frac{1}{7}-\frac{1}{8}\right)=0\\ \Rightarrow x+2010=0\\ \Rightarrow x=-2010\)
Vậy x = -2010
8 tháng 7 2017
\(\frac{x+2015}{5}+\frac{x+2016}{4}=\frac{x+2017}{3}+\frac{x+2018}{2}\)
\(\Leftrightarrow\left(\frac{x+2015}{5}+1\right)+\left(\frac{x+2016}{4}+1\right)=\left(\frac{x+2017}{3}+1\right)+\left(\frac{x+2018}{2}+1\right)\)
\(\Leftrightarrow\frac{x+2020}{5}+\frac{x+2020}{4}-\frac{x+2020}{3}-\frac{x+2020}{2}=0\)
\(\Leftrightarrow\left(x+2020\right)\left(\frac{1}{5}+\frac{1}{4}-\frac{1}{3}-\frac{1}{2}\right)=0\)
\(\Leftrightarrow x+2020=0\)vì \(\frac{1}{5}+\frac{1}{4}+\frac{1}{3}+\frac{1}{2}\ne0\)
\(\Leftrightarrow x=-2020\)
Bài giải
\(\frac{2-x}{2015}+\frac{3-x}{1007}+\frac{4-x}{671}=\frac{2005-x}{2}\)
\(( \frac{2-x}{2015}+1 )+ (\frac{3-x}{1007}+2 )+ ( \frac{4-x}{671}+3 )=\frac{2005-x}{2}+6\)
\(\frac{2017-x}{2015}+\frac{2017-x}{1007}+\frac{2017-x}{671}=\frac{2017-x}{2}\)
\(\frac{2017-x}{2015}+\frac{2017-x}{1007}+\frac{2017-x}{671}-\frac{2017-x}{2}=0\)
\((2017-x)(\frac{1}{2015}+\frac{1}{1007}+\frac{1}{671}-\frac{1}{2})=0\)
Do \(\frac{1}{2015}+\frac{1}{1007}+\frac{1}{671}-\frac{1}{2}\ne0\)
\(\Rightarrow\text{ }2017-x=0\)
\(\Rightarrow\text{ }x=2017\)