Question

Calcule:

a)
[tex]C_{5},_{3}
b)
[tex]C_{7},_{5}
​

Answer 1

a)

$C_5^3 = \cfrac{5!}{3! \cdot 2!} = \cfrac{5 \cdot 4 \cdot 3!}{3! \cdot 2}= 5 \cdot 2 = 10$

b)

$C_7^5 = \cfrac{7!}{5! \cdot 2!} = \cfrac{7 \cdot 6 \cdot 5!}{5! \cdot 2}= 7 \cdot 3 = 21$