**Question:**
A particle moves along a straight line starts at time

seconds with a velocity

. At any subsequent time

seconds the acceleration of the particle is

. Find:

(a) The distance moves before first coming to instantaneous rest,

(b) the total time

seconds taken by the particle to return to the starting point,

(c) the greatest speed of the particle for

.

**My Answers (Without Method):**

(a)

(b)

**My Problem in this question:**

I don't understand part (c). Here is my method:

Greatest speed when

. (At turning point?)

**?!!! **

How would part (c) be done? The correct answer is . Thanks in advance.