Số các tập con $3$ phần tử có chứa $\alpha ,\pi $ của \(C = \left\{ {\alpha ,\beta ,\xi ,\pi ,\rho ,\eta ,\gamma ,\sigma ,\omega ,\tau } \right\}\) là:

$8$

$10$

$12$

$7$

\(x = y = 2.\)    

\(x = y = 2\) hoặc \(x = 2,\,y = 5.\)

\(x = 2,\,y = 5.\)

\(x = 5,\,y = 2\) hoặc \(x = y = 5.\)

\(A = \left\{ {x \in \mathbb{N}\left| {0 \le x \le 8} \right.}\right\}\), \(B = \left\{ {3x \in \mathbb{N}\left| {1 \le x \le 5} \right.} \right\}\), \(C = \left\{ {{2^x} \in \mathbb{N}\left| {1 \le x \le 4} \right.} \right\}\)

\(A = \left\{ {2x \in \mathbb{N}\left| {0 \le x \le 8} \right.} \right\},B = \left\{ {3x \in \mathbb{N}\left| {1 \le x \le 5} \right.} \right\},C = \left\{ {x \in \mathbb{N}\left| {1 \le x \le 16} \right.} \right\}\)

\(A = \left\{ {2x \in \mathbb{N}\left| {x \le 4} \right.} \right\},B = \left\{ {3x \in \mathbb{N}\left| {1 \le x \le 5} \right.} \right\},C = \left\{ {{2^x} \in \mathbb{N}\left| {x \le 4} \right.} \right\}\)

\(A = \left\{ {2x \in \mathbb{N}\left| {x \le 4} \right.} \right\},B = \left\{ {3x \in \mathbb{N}\left| {3 \le x \le 15} \right.} \right\},C = \left\{ {2x \in \mathbb{N}\left| {1 \le x \le 8} \right.} \right\}\)

\(2001\)

\(1001\)

\(1000\)

\(2000\)