Find the instantaneous rate of change, using the definition, of f(x)=5x^2+4x at x=3

Answer 1

The instantaneous rate of change is simply the derivative of f(x) at the given value of x

f(x)=5x²+4x at x=3

f ' (x) = 10x + 4

then plugin x=3

f ' (3) = 10(3) + 4 = 34