Answer:
first of all, the formula given is wrong
it is,
[tex]\sqrt{(x_2-x_1)^2+(y_2-y_1)^2)}[/tex]
so,
let's say
[tex](x_2,y_2)=(-1,1) \\(x_1,y_1)=(3,1)[/tex]
you can choose arbitrarily, answer will be the same
[tex] = \sqrt{(-1-3)^2+(1-1)^2)}\\
=\sqrt{4^2+0}\\
=4[/tex]
