Question

(1+1/2007+1/2008)*(1/2007+1/2008+1/2009)-(1+1/2007+1/2008+1/

Answer 1

先提取公因子：(1/2007+1/2008+1/2009)

即：(1/2007+1/2008+1/2009) * (1+1/2007+1/2008- 1/2007-1/2008)

=(1/2007+1/2008+1/2009) * 1

=1/2007+1/2008+1/2009