A train starts from station `A` with uniform acceleration `a_(1)`. For some distance and then goes with uniform retardation `a_(2)` for some more distance to come to rest at station `B`. The distance between stations `A` and `B` is `4 km` and the train takes `1//5 h` to compete this journey. If accelerations are in km per minute unit, then show that `(1)/(a_(1)) +(1)/(a_(2)) =x`. Find the value of `x`.