practice question synergy

How and why do producers use synergy between product both secondary product and primary products of the same genre to attract audience?

The three posters are similar because they use dull colours to represent each film. Their Genre seems to be Drama, Historic just by looking at the 3 movie posters we can guess this. These poster all use Black, White and one other colour. For example, Lincoln uses Black, White and Gold (which is used for the title of the film). Silver Linings Playbook uses Black, White and Yellow and Argo uses Black, White and Red. All the bright colours stand out and adds a bit of mystery to the posters. All these films as we can tell, must include overcoming hardships of some sort because there is a brighter side behind the dark, dull side. The way that these colours have been used shown implements Drama, crime, Thriller sort of Genre movies- which is what they are. 
The camera shots used in each poster are also similar in some sort of way. Lincoln has a mid-shot side profile which seems to show tension of some kind, Silver Linings Playbook is a close-up shot but only shows half of the characters faces which shows they are both the main characters in this movie and, Argo is in an Extreme close-up view which shows that he is the main character and that there is some mystery/problem behind it. 
All these films also have similar storylines which also explain why they are of similar context. However, one thing they don't have in common is the tagline used in Argo. Argo is the only film out of these three films that has a tagline provided and it is clearly written 'The movie was fake, the mission was real'. This also creates suspense and mystery to the audience and makes them feel anxious to watch them.