Final answer:
The graph of the parabola is increasing from -infinity to 2.5 and decreasing from 2.5 to infinity.
Step-by-step explanation:
To determine where the graph of the parabola is increasing or decreasing, we need to examine the coefficient of the x-term in the equation y = x^2 - 10x.
The coefficient of x^2 is 1, which means the parabola opens upwards. If the coefficient of x^2 is positive, then the graph is increasing on the intervals where x is less than the vertex, and decreasing on the intervals where x is greater than the vertex.
So, the correct answer is D. The graph is increasing from -infinity to 2.5, and decreasing from 2.5 to infinity.