Jawabanmu

2014-09-14T10:52:54+07:00
Dik: r=2t-4t²
      t= 5 sekon
dit: v?
jwb: v= dr/dt
          = d (2t-4t²)/dt
          =2-8t
          =2- 8 (5)
          =2-40
           = -38