[tex] \large \boxed{ \begin{array}{l} \sf{d_{AB} = \sqrt{(x_A - x_B) {}^{2} + (y_A - y_B) {}^{2} } } \\ \\ \sf{d_{AB} = \sqrt{(1 - 1) {}^{2} + (1 - 4) {}^{2} } } \\ \\ \sf{d_{AB} = \sqrt{0 {}^{2} + ( - 3) {}^{2} } } \\ \\ \sf{d_{AB} = \sqrt{0 + 9} } \\ \\ \sf{d_{AB} = \sqrt{9} } \\ \\ \boxed{ \sf{d_{AB} = 3}}\end{array}}[/tex]
