It becomes an addiction when someone is unable to function without the drug. This is called withdraw and comes with side effects like: sweating, lack of sleep, lack of hunger, chills, etc.
For this case we have that by definition, a linear function is of the form 
If we have that a and b are linear functions, then they are of the form:

If we multiply them we have: (Applying distributive property)

That is, we get a quadratic function.
Answer:
