Explain in words why the equation \left(\begin{array}{c}n\\ k\end{array} ight) = \left(\begin{array}{c}n\\ n-k\end{array} ight) is true. Use the definition \left(\begin{array}{c}n\\ k\end{array} ight) = \frac{n!}{k!(n-k)!} to show that the equation in question (1) is true.

Explain in words why the equation .'I is true Use the definition to show that .2 .the equation in question ('I) is true