Find the difference quotient for the following Rational Function f(x)=5/x using the four steps outlined below.

a. find f(x+h)
b. find f(x)
c. substitute f(x+h) and f(x) into the difference quotient formula.
d. simplify

1 answer

f(x+h) = 5/(x+h)
f(x) = 5/x

[f(x+h) - f(x)]/h = [5x -5(x+h)]/[hx(x+h)]

= -5 /[x(x+h) }

= -5/(x^2+hx)

By the way,
if you take the limit of that as h--->0
then you are a calculus student and you just found the derivative
d/dx (5/x) = -5/x^2