14 A new cast contained the statement that the total use of electricity in city A had declined in one billing period by 5%, while household se had declined by 4% and all other uses increased by 25%. Which of the following must be true about the billing period?
answer: "the statement was in error"
why the statement was in error?
47 Suppose that the space S contains exactly eight points. If g is a collection of 250 distinct subsets of S, which of the following statements must be true?
answer: "g has a member that contains exactly one element"
how to get this result?
58 If f(z) is an analytic function that maps the entire finite complex plane into the real axis, then the imaginary axis must be mapped onto
answer: "a point"
does someone know why?
64 Let S be a compact topological space, let T be a topological space, and let f be a function from S onto T. Of the following conditions on f, which is the weakest conditon sufficient to ensure the compactness of T?
(A) f is homeomorphism; (B) f is continuous and 1-1; (C) f is continuous; (D) f is 1-1; (E) f is bounded
why f is 1-1 is not the weakest sufficient condition? and does f bounded imply T is compact?