For an exponential function of the form y = ab^x, where a > 0, the value of b determines whether the function is increasing or decreasing.
If b > 1, then the function is increasing, because as x increases, the value of b^x also increases, causing y to increase.
If 0 < b < 1, then the function is decreasing, because as x increases, the value of b^x decreases, causing y to decrease.
If b = 1, then the function is constant, because b^x = 1 for all values of x.
Therefore, to find values of b that result in a decreasing function, we need to find values of b such that 0 < b < 1.