How to do this
Fill in the blanks to make the equation true (Each blank should contain an integer.)
\binom{n}{k} = \binom{n - 2}{k} + \binom{n - 2}{k - 1} + \binom{n - 1}{k} + \binom{n - 1}{k - 1} + \binom{n}{k - 1} + \binom{n}{k + 1}
