Guys
anyway can anyone explain how to do 12. (a
just letter a

x = 3 seconds

Step-by-step explanation:

The time (x) at which the function reaches its maximum can be determined in couple of ways. If you know calculus, you differentiate the quadratic, set to 0 and solve: . If you do not yet know how to do that, you can just apply the following argument:

The expression will be non-positive for any x. The largest it can be is 0. So the entire function can be at most 23, or less. It is 23 only when and that happens exactly for x=3 (seconds).

As a third option, you can also use a formula for the maximum point of a parabola, but the formula is non-intuitive so I prefer to skip that.

over the argument its not good to fight.

-2

7 - 9 = -2

reversed:

-2 + 9 = 7