AB is the distance between point A and B. Assuming the points on A are x1, y1 and on B are x2, y2 then
AB = √(x2 - x1)^2 + (y2 -y1)^2
where A(6, -1) and point B (7,4) then
AB = √(7 - 6)^2 + (4 - -1)^2
= √(1 + 25)
= √(26)
= 5.099
= 5.10 (to the nearest hundredth place)