A2&A3

 

 

 

 

A2:

 

Adding y-coordinates gives the graph on the left below

 

 

 

 

        

 

 

 

 

 

A3:

 

For the case of a product, if one of the factors is zero so is the product. So, the product will have an x-intercept when either of the factors does. The graph on the right above illustrates this, and you can also see that in an interval where f is constant, the product graph looks just like part of the g graph scaled vertically (and flipped if the multiplier is negative).