Ta có \(6B=1\times3\times6+3\times5\times6+...+97\times99\times6\)
\(=1\times3\times\left(5+1\right)+3\times5\times\left(7-1\right)+5\times7\times\left(9-3\right)+...+97\times99\times\left(101-95\right)\)
\(=1\times3\times5+1.3+3\times5\times7-3\times5\times1+...-97\times99\times95\)
\(=97\times99\times101+3\)
\(\Rightarrow B=\frac{97\times99\times101+3}{6}=161651\)
6B=1x3x6+3x5x6+5x7x6+.....+97x99x6
6B=1x3x(5+1)+3x5x(7-1)+....+97x99x(102-95)
6B=1x3x5+1x3+3x5x7-3x5+....+97x99x101-95x97x99
6B=1x3x97x99x101
6B=969906
=>B=161651
6B = 1x3x6 + 3x5x6 + 5x7x6 +...+ 99x101x6
= 1x3(5+1)+3x5(7-1)+...+97x99(101-95)
= 1x3x5+1x3+3x5x(7-1)+...-97x99x95
=97x99x101+3 rồi tự làm..................... >.<
