From Förberedande kurs i matematik 1

If we use the distance formula

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

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

\displaystyle \begin{align} & d=\sqrt{\left( -2-3 \right)^{2}+\left( 5-\left( -1 \right) \right)^{2}} \\ & =\sqrt{\left( -5 \right)^{2}+6^{2}}=\sqrt{25+36}=\sqrt{61} \\ \end{align}