1x2/x+2x3/x+.+2009x2010/x＝2009
x(1x2/1+2x3/1+.+2009x2010/1)＝2009
x(1-2/1+2/1-3/1+.+2009/1-2010/1)＝2009
x(1-2010/1)＝2009
x(2010/2009)＝2009
x=2010