Lời giải:

\(A=1.3.5.7...99=\frac{1.2.3.4...99.100}{2.4.6.8.100}=\frac{1.2.3...99.100}{(1.2)(2.2)(3.2)...(50.2)}\)

\(=\frac{1.2.3...99.100}{(1.2.3...50).2^{50}}=\frac{51.52...100}{2^{50}}=\frac{51}{2}.\frac{52}{2}....\frac{100}{2}=B\)

ủng hộ mình nha

\(A=1.3.5.7...99=\frac{\left(1.3.5.7...99\right)\left(2.4.6...100\right)}{2.4.6...100}=\frac{1.2.3...100}{\left(2.1\right)\left(2.2\right)...\left(2.50\right)}=\frac{\left(1.2.3...50\right)\left(51.52.53....100\right)}{\left(1.2.3...50\right)\left(2.2.2...2\right)}=\frac{51.52.53...100}{2.2...2}=\frac{51}{2}.\frac{52}{2}.\frac{53}{2}...\frac{100}{2}=B\)

\(R=1.3.5.7...99\)

\(R=\frac{1.2.3.4.5.6.7.8...99.100}{2.4.6.8...100}\)

\(R=\frac{1.2.3.4.5.6..8...99.100}{\left(2.2.2.2...2\right).\left(1.2.3.4...50\right)}\)

\(R=\frac{51.52.53...100}{2.2.2.2...2}\)

\(R=\frac{51}{2}.\frac{52}{2}.\frac{53}{2}...\frac{100}{2}=S\)

Vậy R = S

bó tay chấm com!