Đáp án:
`A<1/4`
Giải thích các bước giải:
`=>A=12/(2.4)^2+20/(4.6)^2+28/(6.8)^2+...+388/(96.98)^2+396/(98.100)^2`
`=>A=12/(2^2. 4^2)+20/(4^2. 6^2)+28/(6^2. 8^2)+...+388/(96^2. 98^2)+396/(98^2. 100^2)`
`=>A=12/4.16+20/16.36+28/36.64+...+388/9216.9604+396/9604.10000`
`=>A=(16-4)/4.16+(36-16)/16.36+(64-36)/36.64+...+(9604-9216)/9216.9604+(10000-9604)/9604.10000`
`=>A=1/4-1/16+1/16-1/36+1/36-1/64+...+1/9216-1/9604+1/9604-1/10000`
`=>A=1/4-1/10000<1/4`
`=>A<1/4`
Vậy `A<1/4`.