Question

for the function f(x)=2/(4-5x)
(a) Use the definition of derivative (limits) to compute f'(2).
(b) Use the result of part a to find an equation of the line tangent tot he curve y= f(x) at the point for which x=2

Answer 1

f'(2) = limit (e approaches 0) of [f(x+e) - f(x)] / e.

f'(2) is the tangent = slope at x=2. From that you can determine the line.