b - d are fine.
For a), it's asking you "when does the car get back to A?", in other words, "when is the distance from A again 0?".
So it's asking you to find t when s = 0.
A car is moving along a straight road. It passes a point A. After t second its distance, s m, from A is given by s = 10t - tsquared
a) find the time when the car passes through A again?
b) find ds/dt? = 10 - 2t
c) find the maximum distance of the car from A.
We need to find ds/dt = 0
10 - 2t = 0
10 = 2t
t = 5 seconds
d) find the speed of the car 3 seconds after the passing of A.
10 - 6 = 4m/s
e) find the acceleration of the car
f''(x) which is -2
Please could someone help with question a) and check the rest? Many thanks in advance.