2x/1*3+2x/3*5+2x/5*7+·····2x/2005*2007=2006
x*(1-1/3+1/3-1/5+...+1/2005-1/2007)=2006
x*(1-1/2007)=2006
2006x/2007=2006
x=2007
2x/1*3+2x/3*5+2x/5*7+·····2x/2005*2007=2006
x*(1-1/3+1/3-1/5+...+1/2005-1/2007)=2006
x*(1-1/2007)=2006
2006x/2007=2006
x=2007