Question

$C^3_1__0 - C^3_9$

Answer 1

Ti-m scris formula combinarilor intr-un raspuns anterior, si o folosim si aici:

$C_{10}^3-C_9^3=\dfrac{10\cdot9\cdot8}{1\cdot2\cdot3}-\dfrac{9\cdot8\cdot7}{1\cdot2\cdot3}=\dfrac{72}{6}\cdot(10-7)=12\cdot3=36$