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 F(x + h) - Rx) (Difference quotient gives the average rate of change.) h The instantaneous rate of change of a function fat the number x is lim (x + h) - F(x) (Taking the limit makes it instantaneous.)