# Math Help - Combinatorics

1. ## Combinatorics

Dear Colleagues,

What is the value of $\binom {20}{0} +\binom {20}{2} +\binom {20}{4} +... \binom {20}{20}$ ?

Best Regards.

2. Originally Posted by raed
Dear Colleagues,

What is the value of $\binom {20}{0} +\binom {20}{2} +\binom {20}{4} +... \binom {20}{20}$ ?

Best Regards.
Hint:

Consider

$(1+1)^{20}$

Use the binomial theorem

3. Originally Posted by raed
Could you please help me in solving the following problem: What is the value of $\binom {20}{0} +\binom {20}{2} +\binom {20}{4} +... \binom {20}{20}$ ?
$\left( {x + y} \right)^n = \sum\limits_{k = 0}^n {\binom{n}{k}x^k y^{n - k} }$.
What if $x=1~\&~y=1~?$

4. Thank you very much for your reply. In fact I tried that but what about terms $\binom {20}{1}, \binom {20}{3},...,\binom {20}{19}$ ?

Best Regards.

5. Originally Posted by raed
Thank you very much for your reply. In fact I tried that but what about terms $\binom {20}{1}, \binom {20}{3},...,\binom {20}{19}$ ?
$x=1~\&~y=-1$ then what?