In order to find the distance between the given points, use the following formula:
where (x1,y1) and (x2,y2) are the coordinates of the points.
In this case, you have:
(x1,y1) = K(1,-1)
(x2,y2) = F(6,-9)
Replace the previous values of the parameters into the formula for d and simplify:
Hence, the distance between K and F points is √89.