A secant is a straight line connecting two points on a curve; therefore, the first thing we need to do is solve for the y values at the two given values of x:
-2log(1)+3 = 3
-2log(1.5)+3 = 2.65
Therefore, the two points are (1,3) and (1.5,2.65).
Slope = rise/run:
Therefore, the slope of the secant line through the points on the curve at x=1 and x=2 is -0.7.