A physicist models the intensity of radiation, III, at a distance x x\,x metres from a point source using the equation
I=25x3+0.4x,x≥1 I = \frac{25}{x^3} + 0.4^x, \quad x \ge 1 I=x325+0.4x,x≥1Find an expression for the rate of change of radiation intensity with respect to distance, dIdx\dfrac{dI}{dx}dxdI.
