Question 120472
Distance formula in {{{R^2}}}: {{{d=sqrt((x[2]-x[1])^2+(y[2]-y[1])^2)}}}

Choice of which point is first does not matter, but you must be consistent.

Choose: {{{x[2]=-6}}}
{{{x[1]=10}}}
{{{y[2]=y[1]=0}}}

Then, 
{{{d=sqrt((-6-10)^2+(0-0)^2)}}}
={{{sqrt((-16)^2)}}}
={{{16}}}