tolong bantu ya..semoga di tambakan ilmu nya

Vektor Posisi

r(t) =  (t³-2t²) i  + (3t²) j

a.
r (3)= (3³ - 2x3²)i + 3(3²) j = 9i + 27i
r(1) = (1-2)i + 3j =  (-) i + 3 j
Veoktor r perpindahan = r(3) - r(1) = (9-(-1) i + (27-3)j = 10i + 24 j
Besar Perpindahan   = √(10²+24²) = 26
arah = α= tan⁻¹ (24/10) = 67,38⁰

b.
kecepatan  v(t) = r'(t)
v(t) = (3t² - 4t) i + (6t)j
v(1) = (-1) i + 6j
v(3) = (15)i + 18j
Besar kecepatan = √15² + 18² = √549= 23,4
arah = α = tan⁻¹(18/15) = 50