5\(\frac{8}{17}\) : x - (\(\frac{8}{17}\)) : x + 3\(\frac{1}{17}\): 17\(\frac13\) = \(\frac{4}{17}\)

(5\(\frac{8}{17}\) - \(\frac{8}{17}\)) : x + \(\frac{52}{17}\) : \(\frac{52}{3}\) = \(\frac{4}{17}\)

5:x + \(\frac{52}{17}\times\) \(\frac{3}{52}\) = \(\frac{4}{17}\)

5 : x + \(\frac{3}{17}\) = \(\frac{4}{17}\)

5 : x = \(\frac{4}{17}\) - \(\frac{3}{17}\)

5 : x = \(\frac{1}{17}\)

x = 5 : \(\frac{1}{17}\)

x = 5 x 17

x = 85

Vậy x = 85

1/1.4 + 1/4.7 + ...+1/x(x+3) = 6/19

3/1.4 + 3/4.7 +..+3/x(x+3) = 18/19

1/1 - 1/4+ 1/4 - 1/7 +...+1/x-1/(x+3) = 1 - 1/19

1- 1/(x+3) = 1 - 1/19

1/(x+3) = 1/19

x + 3 = 19

x = 19 - 3

x = 16

Vậy x = 16

P=\(\frac{2012-1}{2012}+\frac{2013-1}{2013}+\frac{2014-1}{2014}+\frac{2015-1}{2015}\)

  =\(1-\frac{1}{2012}+1-\frac{1}{2013}+1-\frac{1}{2014}+1-\frac{1}{2015}\)

  =\(4-\left(\frac{1}{2012}+\frac{1}{2013}+\frac{1}{2014}+\frac{1}{2015}\right)\)

VẬY P<4

\(\orbr{\begin{cases}\orbr{\begin{cases}\frac{2011}{2012}< 1\\\frac{2012}{2013}< 1\end{cases}}\\\orbr{\begin{cases}\frac{2013}{2014}< 1\\\frac{2014}{2015}< 1\end{cases}}\end{cases}\Rightarrow P< 1+1+1+1=4}\)

\(B=\frac{2012}{2013+2014}+\frac{2013}{2013+2014}< \frac{2012}{2013}+\frac{2013}{2014}\)

\(\Rightarrow A>B\)

\(B=\frac{2012+2013}{2013+2014}=\frac{2012}{2013+1014}+\frac{2013}{2013+1014}\)

Vì: \(\frac{2012}{2013+1014}< \frac{2012}{2013}\)và \(\frac{2013}{2013+2013}< \frac{2013}{2014}\)

\(\Rightarrow A>B\)

~ Rất vui vì giúp đc bn ~