What is the multiplicative rate of change for the exponential function f of x is equal to 2 times 5 halves raised to the negative x power ?

The multiplicative rate of change is the factor by which the function is multiplied when x increases by 1. Since the exponent is negative, (5/2)^(-x) = (2/5)^x, and 2/5 = 0.4. The leading 2 does not change this rate, so the answer is B, 0.4.

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