Consider 1st case, A car starts from rest at a constant acceleration α. It means Acceleration, a1=α initial velocity, u=0 v=u+a1t⇒v0=0+αt1 ⇒v0=αt1...(i) Consider 2nd case, The same car decelerates after some time at a constant acceleration β and comes to rest. It means Acceleration, a2=β Final velocity =0 ⇒v0=βt2...(ii) According to question, t1+t2=t ⇒v0(
1
α
+
1
β
)=t [from Eqs. (i) & (ii)] ⇒v0=
αβt
α+β
...(iii) If we draw the velocity-time graph for the given situation, it will be as follows