解方程：5X/(1*2)+ 5X/(2*3)+ 5X/(3*4) +5X/(4*5) +...+5X/(2003*2004)+ 5X/(2004*2005)=1 .5X(1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+……+1/2003-1/2004+1/2004-1/2005) =1,5X(1-1/2005)=1,5X(2004/2005)=1.所以,X=401/...