In order to find the distance between the given points, use the following formula:
![d=\sqrt[]{(x_2-x_1_{}^{})^2+(y_2-y_1)^2}](https://img.qammunity.org/2023/formulas/mathematics/college/zcadfasqd8b8ua9bdlv7vwvuck5qa3lul8.png)
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:
![\begin{gathered} d=\sqrt[]{(6-1)^2+(-9-(-1))^2} \\ d=\sqrt[]{(5)^2+(-9+1)^2} \\ d=\sqrt[]{25+(-8)^2}=\sqrt[]{25+64} \\ d=\sqrt[]{89} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/n8xg4ltk996d5nro67arrxciktu8bb1zu2.png)
Hence, the distance between K and F points is √89.