The slope of the blue line is -4
How to determine the slope
The slope is represented as m, The slope by definition is the ratio change of the output values to the input values
the slope, m calculating using the points on the graph (5, 4) and (6, 8)
m = (y₀ - y₁) / (x₀ - x₁)
m = (4 - 8) / (5 - 6)
m = (-4) / (41)
m = -4
The slope of the line is 4