1 | initial version |
The reason is that your expression is not equal to zero !!!
If you multiply your expression by $2^{(n+1)}$, and simplify the two bionmials in the middle, you get ${n+1\choose k} - {n\choose k} + {n \choose k-1}$
This can not be zero since ${n+1\choose k} + {~n \choose k-1}$ is usually bigger than ${n\choose k}$ (unless $n=0$ and $k>1$).
2 | No.2 Revision |
The reason is that your expression is not equal to zero !!!
If you multiply your expression by $2^{(n+1)}$, $2^{n+1}$, and simplify the two bionmials in the middle, you get ${n+1\choose k} - {n\choose k} + {n \choose k-1}$
This can not be zero since ${n+1\choose k} + {~n \choose k-1}$ is usually bigger than ${n\choose k}$ (unless $n=0$ and $k>1$).$k>n+1$).