​​​$$\left(a-b\right)^2-\left(a+b\right)^2$$​​

​​​$$\frac{\left(a+b\right)^2}{2}+\frac{\left(a-b\right)^2}{2}$$​​

​​​$$\left(\frac{a+b}{2}\right)^2-\left(\frac{a-b}{2}\right)^2$$​​

​$$x = a^n$$​​

​$$x = Inx$$​​

​$$a = x^n$$​​

​$$x² – y²$$​​

​$$x + y$$​​

​$$\frac{1}{2}\:\left(a\:-\:b\right)\:h$$​​

​$$\frac{n\left(n\:+\:1\right)}{2}$$​​

​$$\frac{n\left(n\:+\:1\right)\:\left(2n\:+\:1\right)}{2}$$​​