Question

докажите неравенства ​

Answer 1

$\boldsymbol{A^5_{15}:P_5=\dfrac{15!}{(15-5)!}:5!=\dfrac{15!}{5!\cdot (15-5)!}=\dfrac{15!}{5!10!}=C^{5}_{15}=C^{10}_{15}}$