Question

Calcula-se a combinação de:
a. $C^5_2$
b. $C^1^2_7$

Answer 1

$\displaystyle \binom{5}{2}=\frac{5\times 4}{1\times 2}=10\\ \\ \binom{12}{7}= \frac{12\times11\times10\times9\times8\times7\times6}{1\times2\times3\times4\times5\times6\times7}=\frac{11\times10\times9\times8}{2\times5}=792$