Question 990216
F(a)=(a)/2+3
F(a+h)=(a+h)/2 +3
{F(a+h)-F(a)}/h
and (a+h)/2+3-(a/2)-3=(a/2)+(h/2)-(a/2)=h/2
That is divided by h=(1/2)
As h approaches 0, it is not a factor.  
The slope is (1/2).