#"1- we must find distance between the point of (7,-8,1)"##" and (-1,4,-6)"# #Delta s=sqrt((-1-7)^2+(4+8)^2+(-6-1)^2)# #Delta s=sqrt(64+144+49)" "Delta s=sqrt257 " m"# #"2- now, we can calculate speed using : " v=(Delta s)/(Delta t)# #v=sqrt 257/2# #v~=8,02 m/s#