Question 4893
Any squared term is a parabola... In this case it begins at zero, because you don't have a negative time

Treat your x axis as the t in this case, plug in a couple of numbers for the first equation:
If t=0, y = 0  (Plot (0,0))
If t=1, y = 4  (Plot (1,4))
Connect these two with a curving line (like the bottom of a bowl)

the second equation begins at 2 seconds and will be shaped like an upside down bowl
-4t^2+32t-32
If t=2, then y=-48  (plot 2,-48)
-4(2)^2+32(2)-32=-48
If t=6 then y=16 (plot 6,16)
-4(6)^2+32(6)-32=16

The third one will have the same shape as the first: a parabola opening upward, extending to the right:

4(t)^2-64t+256
If t=6 then y=16  (plot(6,16))
If t=8 then y=0  (plot (8,0))

You can always just plug more numbers into your equation if you are unsure of the shape of it.