Aus Online Mathematik Brückenkurs 1

If we use the distance formula

\displaystyle d=\sqrt{(x-a)^2+(y-b)^2}

to determine the distance between the points \displaystyle (x,y) = (-2,5) and \displaystyle (a,b) = (3,-1), we get

\displaystyle \begin{align} d &= \sqrt{(-2-3)^2+(5-(-1))^2}\\[5pt] &= \sqrt{(-5)^2+6^2}\\[5pt] &= \sqrt{25+36}\\[5pt] &= \sqrt{61}\,\textrm{.} \end{align}