Hi all
1 ) why A verage acceleration is the slpoe of the velocity ?
2 ) why the velocity decreases when the acceleration is negative ?
1. because of the definition of average acceleration ...
$\displaystyle \bar{a} = \frac{\Delta v}{\Delta t}$
2. because ...
when the rate of change of a quantity is negative, that quantity decreases.
when the rate of change is positive, it increases.
when the rate of change is zero, it remains constant.
... all of these ideas should be in your textbook.