The numbers that are raised to an exponent are called bases, when the base is less than one, the function represents an exponential decay and when the base is more than one, the function represents an exponential growth.
a) In the function y = (1/2)^x, the base is 1/2, because this is the number that is raised to x, since 1/2 (0.5) is less than 1, this function represents an exponential decay.
b) In the function y=0.4*(1.1^x) the base is 1.1, because this is the number that is raised to x, since 1.1 is more than 1, this function represents an exponential growth.