If the image of a positive scale function passes through points (2,4), then the analytic expression of the function is______ .

If the image of a positive scale function passes through points (2,4), then the analytic expression of the function is______ .

Let the analytic expression of the function be y = KX (K ≠ 0), and substitute (2, 4) to get: 2K = 4, the solution is: k = 2, so the analytic expression of the function is: y = 2x