已知m=2005,求m/(1x2)+m/(2x3)+m/(3x4)...+m/(2003x2004)+m/(2004x2005)的值.

来源:学生作业帮助网 编辑:作业帮 时间:2024/04/28 03:12:00
已知m=2005,求m/(1x2)+m/(2x3)+m/(3x4)...+m/(2003x2004)+m/(2004x2005)的值.

已知m=2005,求m/(1x2)+m/(2x3)+m/(3x4)...+m/(2003x2004)+m/(2004x2005)的值.
已知m=2005,求m/(1x2)+m/(2x3)+m/(3x4)...+m/(2003x2004)+m/(2004x2005)的值.

已知m=2005,求m/(1x2)+m/(2x3)+m/(3x4)...+m/(2003x2004)+m/(2004x2005)的值.
m/(1×2)+m/(2×3)+m/(3×4)+...+m/(2003×2004)+m/(2004×2005)
=m[1/(1×2)+1/(2×3)+1/(3×4)+...+1/(2003×2004)+1/(2004×2005)]
=m(1-1/2+1/2-1/3+1/3-1/4+...+1/2003-1/2004+1/2004-1/2005)
=m(1-1/2005)
=2004m/2005
=2004×2005/2005
=2004

∵1/[n(n+1)]=1/n-1/(n+1),
∴m/(1x2)+m/(2x3)+m/(3x4)...+m/(2003x2004)+m/(2004x2005)
=m[1/1-12/2+1/2-1/3+1/3-1/4+…+1/2004-1/2005]
=m(1-1/2005)
=2004m/2005

当m=2005时,
原式=2004。