Question

a. For the following function, find f (a).

b. Determine an equation of the line tangent to the graph of f at (a,f(a)) for the given value of a.
f(x)= 9/(x+4) ,a=6

Answer 1

didn't we do this already?

f(a) = 9/(a+4)

find f'(2). That is the slope of your tangent line. Then its equation is
y-f(2) = f'(2) (x-2)