Final answer:
The subject related to this question is Geometry. To find the area of a square with sides of length x that varies with time t, we use the formula A = x^2 in Geometry.
Step-by-step explanation:
The subject related to the question is Geometry. Calculating the area of a square involves using geometric principles. In this case, we need to find the area of a square with sides of length x where x varies with time t.
To find the area of a square, we use the formula A = x^2, where A represents the area and x represents the length of one side of the square. The formula is derived from the fact that the area of a square is equal to the side length squared.
Therefore, the answer is Geometry.