Question

C^4 10= C^6 10= 10!/4!(10-4!)= 4•5•6•7•8•9•10/4!•12•3•4•5•6=7•2•3•5=210

Answer 1

$C_{10}^4=\frac{10\cdot 9\cdot 8\cdot 7}{4!}=\frac{10\cdot 9\cdot 8\cdot 7}{1\cdot 2\cdot 3\cdot 4}=10\cdot 3\cdot 7=210\\\\C_{10}^6=C_{10}^{10-6}=C_{10}^4=210$

Или:  $C_{10}^4=\frac{10!}{4!\, \cdot \, 6!}=\frac{6!\, \cdot 7\cdot 8\cdot 9\cdot 10}{4!\, \cdot \, 6!}=\frac{7\cdot 8\cdot 9\cdot 10}{1\cdot 2\cdot 3\cdot 4}=210$  .