Question 840784
Use the distance formula,
{{{D^2=(x[2]-x[1])^2+(y[2]-y[1])^2}}}
{{{D^2=(-9-(-8))^2+(-13-5/7)^2}}}
{{{D^2=(-9+8)^2+(-91/7-5/7)^2}}}
{{{D^2=(-1)^2+(-96/7)^2}}}
{{{D^2=1+9216/49}}}
{{{D^2=49/49+9216/49}}}
{{{D^2=9265/49}}}
{{{D=sqrt(9265/49)}}}
{{{D=(1/7)*sqrt(9265)}}}