An equation that represents the graph shown include the following: A. f(x) = -x + 2.
In Mathematics and Geometry, the point-slope form of a straight line can be calculated by using the following mathematical equation (formula):

Where:
- x and y represent the data points.
- m represent the slope.
First of all, we would determine the slope of the line by using these points (1, 1) and (0, 2);

Slope (m) = (2 - 1)/(0 - 1)
Slope (m) = 1/-1
Slope (m) = -1
At data point (0, 2) and a slope of -1, a function for this line can be calculated by using the point-slope form as follows:

y - 2 = -1(x - 0)
y - 2 = -x
y = -x + 2
f(x) = -x + 2