Answer:
OPTION 4
Explanation:
Let be f(x) the function that represents the area of Triangle A:

Let be g(x) the function that represents the area of Triangle B:

Then, you need to add the area of Triangle A and the area of Triangle B in order to find the sum of the areas (Let be h(x) the function that represents the sum of the the areas of triangles A and B):
Therefore, this is:

You can notice that this matches with the option 4.