1-2-3+4-5-6+7-8-9+.+2002-2003-2004=?
9个回答

1-2-3+4-5-6+7-8-9+.+2002-2003-2004

=(1+4+7+...+2002)-(2+5+8+...+2003)-(3+6+9+...+2004)

=(1+2002)*668/2-(2+2003)*668/2-(3+2004)*668/2=671006