Answer: The required term to be added is

Step-by-step explanation: We are given the following product :

We are to find the expression that must be added to (x² - 3x) to get the final answer.
To find the product, we need to multiply each term of the first expression (x - 3) to each factor of the second expression (x + 4).
We have

where

Therefore, to get the final answer, we need to add the following expression :

Thus, the required term to be added is
