`B= 12/(2.4)^2 + 20/(4.6)^2 +...+ 388/(96.98)^2 + 396/(98.100)^2`
`B= 12/(2^2 . 4^2) + 20/(4^2 . 6^2) + ...+ 388/( 96^2 . 98^2) + 396/(98^2 . 100^2)`
`B= 12/4.16 + 20/16.36 + ...+ 388/9216.9604 + 396/9604.10000`
`B= 1/4- 1/16 + 1/16- 1/36 + ...+1/9216 - 1/9604 + 1/9604 - 1/10000`
`B= 1/4- 1/10000 < 1/4`
Vậy `B<1/4`