a)
In general, we say that a function f(x) is positive on an interval (a,b) if
[tex]f(x)>0,x\in(a,b)[/tex]In other words, the positive parts of a function are those sections of it above the x-axis.
Therefore, in our case,
[tex]function\text{ }positive:(-\infty,-1)\cup(0,1)\cup(2.5,\infty)[/tex]b)
On the other hand, a function is decreasing on a certain interval if its derivative on such interval is less than zero.
Therefore, we need to identify the intervals at which the graph is decreasing by using the definition below
[tex]\begin{gathered} f(x)\text{ decreasing on }(a,b) \\ \Rightarrow f(x)>f(y);xThus, in our case, the function is decreasing on[tex]function\text{ }decreasing:(-\infty,-0.6)\cup(0.5,2)[/tex]Notice that -0.6 is just an approximation because we cannot know the exact value of the leftmost minimum of the function due to the lack of accuracy of the grid.