Question

A particle moves along the x-axis so that at time t ≥ 0 its position is given by v(t) = 6t^2 - 84t -90. Determine all intervals when the acceleration of the particle is negative.

Answer 1

The acceleration $a(t)=12t-84$

$12t-84<0$

$12t<84$

$t<7$

Answer: the acceleration of the particle is negative when $t<7.$