Differentiation ---------------＊

s = t^3 + 3t + 4
Velocity = ds/dt
= 3t² + 3
At t = 3, ds/dt = 3*3²+3
= 3*9+3
= 30
So the velocity after 3 seconds is 30 cm/s.

Acceleration = d²s/dt²
= 6t
At t = 3, d²s/dt² = 6*3 = 18
So the acceleration after 3 seconds is 18 cm/s².

(Since the question asks for velocity and acceleration, the answers should be expressed with the correct units.)

velocity: ds/dt|t=3

=(dt^3/dt + 3dt/dt)|t=3

=(3t^2+3)|t=3

=3(3^2)+3

=30

acceleration: d^2 s/dt^2 |t=3

=d(3t^2+3)/dt |t=3

=3dt^2/dt |t=3

=6t |t=3

=6*3

=18