1 + 1/3 + 1/6 + 1/10 + ... + 2/x(x + 1) = 4007/2004
2/2 + 2/6 + 2/12 + 2/20 + ... + 2/x(x + 1) = 4007/2004
2 × (1/1×2 + 1/2×3 + 1/3×4 + 1/4×5 + ... + 1/x(x + 1)) = 4007/2004
1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + ... + 1/x - 1/x + 1 = 4007/2004 : 2
1 - 1/x + 1 = 4007/2004 × 1/2
x/x + 1 = 4007/4008
=> x = 4007
\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{2}{x.\left(x+1\right)}=\frac{2003}{2005}\)
Tìm số tự nhiên n biết: \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{2}{n\left(n+1\right)}=\frac{2003}{2004}\)
Tìm số tự nhiên n biết: \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{2}{n.\left(n+1\right)}=\frac{2003}{2004}\)
Tìm số tự nhiên x biết \(1+\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{2}{x\left(x+1\right)}=1\frac{2003}{2005}\)
1 tìm x thuộc N biết
\(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...................+\frac{1}{x\left(x+1\right):2}=\frac{2001}{2003}\)
Tìm x biết : \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+..,+\frac{2}{x\left(x+1\right)}=\frac{2004}{2005}\)
Tìm x biết: \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{2}{x.\left(x+1\right)}=\frac{2004}{2005}\)
Bài 1:Tìm x
2+\(\frac{2}{6}\)+\(\frac{2}{12}+\frac{2}{20}+........+\frac{2}{x\left(x+1\right)}=1\frac{2005}{2007}\)
Bài 2 :So sánh
a,\(\frac{2003}{2004}+\frac{2004}{2005}+\frac{2005}{2003}\)với 3
b,\(\frac{2005.2006}{2005.2006+1}\)và \(\frac{2006.2007}{2006.2007+1}\)
Tìm số nguyên x biết: \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{1}{x.\left(x+1\right)}=\frac{2004}{2005}\)
