C6 10*C7 10+C8 10 +C9 10+ C10 10 GIÚP EM VỚI Ạ E ĐANG CẦN GẤP <3

$C_{10}^6.C_{10}^7+C_{10}^8+C_{10}^9+C_{10}^{10}$

$=\dfrac{10!}{6!.4!}.\dfrac{10!}{7!.3!}+\dfrac{10!}{8!.2!}+\dfrac{10!}{9!}+1$

$=\dfrac{10.9.8...1}{1.2...6.4!}.\dfrac{10.9.8...1}{1.2...7.3!}+\dfrac{10.9.8...1}{1.2....8.2!}+10+1$

$=\dfrac{7.8.9.10}{4!}.\dfrac{8.9.10}{3!}+\dfrac{9.10}{2!}+11$

$=\dfrac{5040}{24}.\dfrac{720}{6}+\dfrac{90}{2}+11$

$=210.120+45+11$

$=25256$