Work Step by Step
Velocity is a function of t. We found in (a) that $v(t)=-12+6t$. This is a linear function with positive slope. At t=1, the velocity is negative ($-6m/s$), and it gets less negative, until the moment in time t=2s, when it becomes zero (after which it becomes positive and increases). The speed, being the MAGNITUDE of velocity, is thus, momentarily 6 m/s and approaching zero (until the moment t=2) after which it will increase from zero. Therefore, to answer the question, at t=2s, the speed is decreasing.