Aparticle moves on a coordinate line with acceleration startfraction d squared s over dt squared endfraction equals 45 startroot t endroot minus startfraction 15 over startroot t endroot endfraction , subject to the conditions that startfraction ds over dt endfraction equals 9 and sequals12 when t equals 1. find the velocity v equals startfraction ds over dt endfraction in terms of t and the position s in terms of t.