Use the formula below to find the instantaneous rate of change of the function at the given x-value. f(x) = 5x + 4 at x = 7 Average and Instantaneous Rate of Change The average rate of change of a function f between x and x + h is R( x + h) - f(x) (Difference quotient gives the average rate of change.) h The instantaneous rate of change of a function f at the number x is lim R( x + h) - R(x) (Taking the limit makes it instantaneous.) h-0 h