B = 12/(2.4)2 + 20/(4.6)2 + … 388/(96.98)2 + 396/(98.100)2
B = (2.2+4.2)/(2.4)2 + (4.2+6.2)/(4.6)2 + … (96.2+98.2)/(96.98)2 + (98.2+100.2)/(98.100)2
B = 2.2/(2.4)2+4.2/(2.4)2 + 4.2/(4.6)2+6.2/(4.6)2 + ... + 96.2/(96.98)2+98.2/(96.98)2 +98.2/(98.100)2+100.2/(98.100)2
B = 1/4+1/2+1/6+1/4+...+1/98+1/96+1/100+1/98>1/4
Vậy B>1/4