Mmm.
The red tangent and the blue secant both have the same slope.
I will look at the blue secant.
a) does it have a positive or a negative gradient?
It goes through the points (0,-2) and (1,1)
b) What is the rise between these points?
c) what is the run?
d) So ... What is the gradient?
Of course, you count the 0 line :)