1/1*2*3*4+1/2*3*4*5...+1/11*12*13*14
=(1/1*2*3-1/2*3*4+1/2*3*4-1/3*4*5...+1/11*12*13-1/12*13*14)÷3
=(1/1*2*3-1/12*13*14)÷3
=(1/6- 1/2184)÷3
=363/21984÷3
=121/2184
2004*794减589分之205+794*2003
= 2003*794+794减589分之205+794*2003
= 2003*794+205分之205+794*2003
=1