(a) Explain why calculating 22.5 is a square-root problem. What does 20.3 mean? (b) Verify that (-8)1/3 can be evaluated, but that (-8)1/4 cannot, and explain why (-8)2/6 is ambiguous. To avoid difficulties like these, it is customary to restrict the base, b, of an exponential function, f(x) = b, to be a positive number.