[tex]MN=\sqrt {(x_{N}- x_{M} )^{2}+(y_{N}- y_{M} )^{2} }[/tex]
[tex]MN=\sqrt {[3- (-3) ]^{2}+[4-(-4)]^{2} }[/tex]
[tex]MN=\sqrt {(3+3)^{2}+(4+4)^{2} }[/tex]
[tex]MN=\sqrt {6^{2}+8^{2} }[/tex]
[tex]MN=\sqrt {36+64}[/tex]
[tex]MN=\sqrt {100 }[/tex]
[tex]MN=10 u.m.[/tex]