Let’s consider AD be the median through A.
As we know that, AD is the median and D is the mid-point of BC
Therefore, the coordinates of D are $(1+5/2,-1+1/2)=(3,0)$
So,
Length of median $AD=\sqrt{\left[ {{(3+1)}^{2}}+{{(0-3)}^{2}} \right]}$
$=\sqrt{\left[ {{\left( 4 \right)}^{2}}+{{(-3)}^{2}} \right]}$
$=\sqrt{(16+9)}$
$=\sqrt{25}$
$=5$ units