## anonymous one year ago Evaluate the sum of series from (k=o to 5 ) (-1)^k combination of (5 k)

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1. anonymous

$\sum_{k=0}^{3} \left(\begin{matrix}3 \\ k\end{matrix}\right) (-1)^{k}$ Evaluate this using binomial thorem please. $\sum_{k=0}^{n} \left(\begin{matrix}n \\ k\end{matrix}\right) a ^{n-k}b ^{k}$

2. anonymous

Since the last sum is equivalent to $$(a+b)^n$$, you can simply set $$a=1$$ and $$b=-1$$, with $$n=3$$. What's $$1-1$$?