Question

Tính:\(A=\frac{1}{1^4+1^2+1}+\frac{2}{2^4+2^2+1}+...+\frac{2014}{2014^4+2014^2+1}\)

 

Answer 1

Phân số tổng quát 

\(\frac{x}{x^4+x^2+1}=\frac{x}{\left(x^2-x+1\right)\left(x^2+x+1\right)}\)

với x = 1;2;...;2014 ta có :

A  = \(\frac{1}{1.3}+\frac{2}{3.7}+\frac{3}{7.13}+....+\frac{2014}{4054183.4058211}\)

A = \(\frac{1}{2}\left(\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{7}+...+\frac{1}{4054183}-\frac{1}{4058211}\right)\)