Calculate Area Under (x-3)²: Quadratic Function Analysis

To determine where the function $y = (x-3)^2$ is increasing, consider the following:

• The function is a parabola that opens upwards, centered at the vertex $x = 3$.
• A parabola of the form $y = (x-p)^2$ is increasing on the interval $x > p$.

This means the function $y = (x-3)^2$ begins to increase after the vertex, which is at $x = 3$.

Thus, the area of increase (or ascending area) for this function is when $x > 3$.

Therefore, the correct answer is $3 < x$.