Given equation is : [tex]x^{2}-4=0[/tex]
Solving it we get,
[tex]x^{2}=4[/tex]
[tex]\sqrt{x}=\sqrt{4}[/tex] and [tex]\sqrt{x}=-\sqrt{4}[/tex]
This gives [tex]x=2[/tex] and [tex]x=-2[/tex] or we can say the roots are [tex](x+2)(x-2)[/tex]
Here Stefan is right, the root has a multiplicity of 1.