ta có:1=1
1/2+1/3<1/2+1/2=1
1/4+1/5+...+1/7(co 4 p/số)<1/4+1/4+1/4+1/4=4/4=1
1/8+..+1/15(c0 8 p/số)<1/8+1/8+...+1/8(co 8 p/số)=8/8=1
1/16+...+1/31(co 16 phan so)<1/16+...+1/16(co 16 p/số)=16/16=1
1/32+...+1/63(có 32 p/số)<1/32+...+1/32(có 32 phân số)=32/32=1
Do đó B<1+1+1+1+1+1=6
DUYỆT MK NHA BẠN