A rule that defines the function graphed above include the following: A. y = 2x + 3; y = -1/3(x) + 3.
In Mathematics and Geometry, the slope-intercept form of the equation of a straight line refers to the general equation of a linear function and it is represented by this mathematical equation;
y = mx + b
Where:
- m represents the slope.
- x and y are the points.
- b represents the y-intercept.
First of all, we would determine the slope of the upward sloping line by using these points (0, 3) and (-1, 1);

Slope (m) = (1 - 3)/(-1 - 0)
Slope (m) = -2/-1
Slope (m) = 2
At y-intercept (0, 3) and a slope of 2, an equation for this line can be calculated by using the slope-intercept form as follows:
y = mx + b
y = 2x + 3
For the slope of the downward sloping line, we have;
Slope (m) = (2 - 3)/(3 - 0)
Slope (m) = -1/3
At y-intercept (0, 3) and a slope of -1/3, an equation for this line can be calculated by using the slope-intercept form as follows:
y = mx + b
y = -1/3(x) + 3