8又三分之二×5+8又七分之五×21+三分之一×5—8又3分之二×21
=(8又2/3+1/3)×5+8×21+5/7×21-8×21-2/3×21
=9*5+8*21+15-8*21-14
=45+15-14
=46
15分之1+35分之1+63分之1+99分之1
=1/2*(2/15+2/35+2/63+2/99)
=1/2*(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11)
=1/2*(1/3-1/11)
=1/2*8/33
=4/33
8又三分之二×5+8又七分之五×21+三分之一×5—8又3分之二×21
=(8又2/3+1/3)×5+8×21+5/7×21-8×21-2/3×21
=9*5+8*21+15-8*21-14
=45+15-14
=46
15分之1+35分之1+63分之1+99分之1
=1/2*(2/15+2/35+2/63+2/99)
=1/2*(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11)
=1/2*(1/3-1/11)
=1/2*8/33
=4/33