A body starting from rest travels in a straight line, first with uniform accelerationaand then with uniform decelerationb.

It comes to rest when it has covered a total distanced.

If the overall time for the journey isT, show that t^2 =2d (1/a +1/b)

i have the solution to the question but cant understand it as the person who did them doesnt have clear writing and also didnt explain everything he did here is the link.

http://thephysicsteacher.ie/Exam%20M...ation/1979.pdf its the second question on the link can somebody explain how he writes distance under the curve=2d . it says the total distance travelled was d so why did he say 2d. also how did he come up with t1=(b/b+a)T