1/2x3/2+1/3x4/2+1/4x5/2+1/5x6/2+.......+2/Xx(X+1)=2011/2013
2/2x3+2/3x4+2/4x5+2/5x6+.....+2/Xx(X+1)=2011/2013
2x(1/2x3+1/3x4+1/4x5+1/5x6+....+1/Xx(x+1)=2011/2013
1/2x3+1/3x4+1/4x5+1/5x6+....+1/Xx(X+1)=2011/4026
1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+.....+ 1/x-1/x+1=2011/4026
1/2-1/x+1=2011/4026
1/x+1=1/2-2011/4026
1/x+1=1/2013
Suy ra x=2012
tìm x
1+ 1/3+1/6+1/10+...+1/x(x+2):2=1+ 2009/2011
1/3+1/6+1/10+........+2/x(x+1)=2011/2013
1/3+1/6+1/10 +...+2/ x.(x+1)=2011/2013
Tìm x biết 1+1/3+1/6+1/10+...+1/x(x+2):2=2009/2011
1/1 + 1/3 + 1/6 + 1/10 + 1/x.(x+1) : 2 = 2010/2011
tìm x
Tìm x€z, biết: 1/3+1/6+1/10+...+1/x(x+1):2=2009/2011
Tìm x:
1\3+1\6+1\10+...+2\x.(x+11) = 2009\2011
Tìm x biết : 1+1/3+1/6+1/10+...+1/x(x+1):2=1+2009/2011
\(\dfrac{1}{3}\)+\(\dfrac{1}{6}\)+\(\dfrac{1}{10}\)+...+\(\dfrac{2}{x\left(x+1\right)}\)=\(\dfrac{2011}{2013}\)
