Ta có:
$C$ $=$ $1$. $3$ . $5$ $.....$ $99$
$C$ $=$ $1$ . $2$ . $3$ .... $100$ : $2$: $4$:.... : $100$
$C$ $=$ $\dfrac{1.2....99.100}{2.4...100}$
$C$ $=$ $\dfrac{1.2.3...99.100}{(2.1)( 2.2) .( 2.3).....( 2.50)}$
$C$ $=$ $\dfrac{(1.2.3.4...50)(51.52.53.....100)}{(1.2.3...50).( 2.2.2...2)}$
$C$ $=$ $\dfrac{51.52.53...100}{2.2.2....2}$
$C$ $=$ $\dfrac{51}{2}$ $.$ $\dfrac{52}{2}$ $.$ $\dfrac{53}{2}$ $...$ $\dfrac{100}{2}$
⇒ $C$ $=$ $D$
Chúc học tốt!
