[tex]A = (-1,2) \ \ \rightarrow \ \ x_{A} = -1, \ \ y_{A} = 2\\B = (3,8) \ \ \rightarrow \ \ \ \ x_{B} =3, \ \ y_{B} = 8[/tex]
Długość odcinka o końcach w punktach: [tex]A=(x_{A}, y_{A}), \ \ B=(x_{B}, y_{B})[/tex]
[tex]|AB| = \sqrt{(x_{B}-x_{A})^{2}+(y_{B}-y_{A})^{2}}}\\\\\\|AB| = \sqrt{(3-(-1))^{2}+(8-2)^{2}} = \sqrt{4^{2}+6^{2}} = \sqrt{16+36} = \sqrt{52} = \sqrt{4\cdot13} =\\\\=\boxed{ 2\sqrt{13}}[/tex]
