2/3+4/5+8/9+16/17+32/33+64/65+128/129+256/257+512/513
=(1+2/1)+(1+4/1)+(1+8/1)+(1+16/1)+(1+32/1)+(1+64/1)+(1+128/1)+(1+256/1)+(1+512/1)
=(1+1+1+1+1+1+1+1+1)+(2/1+4/1+8/1+16/1+32/1+64/1+128/1+256/1+512/1)
=9+512/511
=9又512分之511