Tim x:
x . (1/2+1/3+1/4+. . .+1/2011+1/2012)
2012/1 +2011/2+2010/3+2009/4+2/2011+1/2012
=1
tính tổng các số sau: -2012; -2011; -2010; -2009;...; -1; 0; 1; 2; 3; 4;...;2009; 2010; 2011; 2012
( 2009/2010 + 2010/2011 + 2011/2012 ) x ( 1/3 - 1/4 - 1/12 )
tìm x,biet(1/2+1/3+.............+1/2012+1/2013).x=2012/1+2011/2+2010/3+......+2/2011+1/2012
Tìm x biết (1/2+1/3+...+1/2012+1/2013).x = 2012/1+2011/2+2010/3+...+2/2011+1/2012
So sánh P và Q biết : P = 2010/2011 + 2011/2012 + 2012/2013 và Q = 2010+2011+2012/ 2011 +2012+2013
Chứng tỏ N < 1 với N = \(\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+...+\frac{1}{2009^2}+\frac{1}{2010^2}\)
Cho P = 1/2 + 1/3 +1/4 +...+1/2011 + 1/2012
Q = 1/2011 + 2/2010 + 3/2009 +...+ 2009/3 + 2010/2 + 2011/1
tìm X biết : ( 1 / 2 + 1/3 + ........+ 1 /2012 + 1/2013 ) . x = 2012/1 + 2011/2 + 2010 /3 + .....+2/2011+1/2012
tìm x (1/2+1/3+...+1/2013) *x= 2012 +2011/2+2010/3+...+2/2011+1/2012
