$\sum_{i=0}^{n}{\prod_{j=0\\j\not=i}^{n}\frac{x-x_j}{x_i-x_j}}=1$
77712
Lagrange polynomials sum to one
55339
Find the sum $\sum_{n=1}^{\infty}\frac{ 1}{n^{2}(2n-1)}$
562
Formula for calculating $\sum_{n=0}^{m}nr^n$
50972
Prove that $\sum_{x=1}^{n} \frac{1}{x (x+1)(x+2)} = \frac{1}{4} - \frac{1}{2 (n+1) (n+2)}$
84949
Evaluate $\prod_{n=1}^\infty \frac{2^n-1}{2^n}$
77510
$\sum_{1}^{n}\left ( a_{i}b_{i} \right )\geq \prod_{1}^{n}\left ( a_{i}^{b_{i}} \right )$
78033
Evaluating $\prod_{n=1}^{\infty}\left(1+\frac{1}{2^n}\right)$
137027
Find the value of $\sum_{n=0}^\infty\frac{1}{9n^2+9n+2}$
14197
show that $\sum_{i=0}^l \dfrac{{l\choose i}}{{n\choose k + i}} = \dfrac{n+1}{(n-l+1) {n-l\choose k}}$
69498
What is $\sum_{r=0}^n \frac{(-1)^r}{\binom{n}{r}}$?
63474
Showing $\sum_{i = 1}^n\frac1{i(i+1)} = 1-\frac1{n+1}$ without induction?
126105
Compute $\sum_{k=1}^{n} \frac 1 {k(k + 1)} $
9246
Calculating $\prod (\omega^j - \omega^k)$ where $\omega^n=1$.
14968
How $\frac{1}{n}\sum_{i=1}^n X_i^2 - \bar X^2 = \frac{\sum_{i=1}^n (X_i - \bar X)^2}{n}$
108401
Sum of binomial coefficients $\sum_{k=0}^{n}(-1)^k\binom{n}{k}\binom{2n - 2k}{n - 1} = 0$
44621
Simple binomial theorem proof: $\sum_{j=0}^{k} \binom{a+j}j = \binom{a+k+1}k$
154544
Prove that $ \sum_{n=0}^\infty \frac{z^{2^n}}{1-z^{2^{n+1}}}=\frac{z}{1-z} $