[i]Ms. Azizah experimented to determine the speed of a trolley along a straight track. The velocity, [/i][math]v[/math][math]ms^{-1}[/math][i] , of the trolley at a [/i][math]t[/math][i] time instant after passing a fixed point [/i][math]O[/math][i] is given by [/i][math]v=t^2-7t+6[/math][i][br][br][Assume the motion to the right as positive.][br][/i][br][i](a) Find[br] (i) the initial velocity, in [/i][math]cms^{-1}[/math][i] , of the trolley,[br][/i]

[i](ii) the time interval, in seconds, when the trolley moves to the left,[/i]

[i](iii) the time interval, in seconds, when the acceleration of the trolley is positive[/i]

[i](b) Sketch the velocity-time graph for the movement of the trolley for[/i]