User:Wilson shao~enwiki

$$\left(\sum_{i=1}^n x_i y_i\right)^2\leq \left(\sum_{i=1}^n x_i^2\right) \left(\sum_{i=1}^n y_i^2\right)$$

$$\int_{a}^{a+mb} f\left(x\right)\,dx = \lim_{n\rightarrow \infty} \sum_{k=1}^{mn} \frac{b}{n} f\left(a+\frac{kb}{n}\right)$$

$$y[n] = \frac{2}{5}\sum_{k=0}^{4}x[n-k]$$