Use point-slope form:
y - y1 = m(x - x1)
Calculate the slope of the given line to find the value of m:
m = (y2 - y1)/(x2 - x1) = (0 - (-1))/(2-0) = 1/2
Choose a point on the line for x1 and y1. We will use the point (2,0).
Substitute 1/2 for m, 2 for x1, and 0 for y1:
y - 0 = (1/2)(x-2)
y = (1/2)x - 1
Therefore, f(x) = (1/2)x - 1.