x(1/1*2+1/2*3+1/3*4+……+1/2005*2006)=2005
x(1-1/2+1/2-1/3+1/3-1/4+……+1/2005-1/2006)=2005
x(1-1/2006)=2005
(2005/2006)x=2005
x=2006