44. if x is a real number and P is a polynomial function, then lim h-> (P(x+3h)+P(x-3h)-2P(x))/h^2=?
答案选D, 9p‘’(x)。 我想选E,无穷。
我的理由:因为一开始分子分母全为0,所以用罗比达法则。求完一次导,分子变为3P‘(x+3h)-3P’(x-3h)-2P‘(x), 当h趋于0时,分子趋于-2P’(x)。 而分母为2h,当h趋于无穷,其趋于零。这样这个极限难道不是无穷吗?
62. let R be the set of real numbers with the topology generated by the basis {[a,b):a<b,where a,b 属于R}. if x is the subset [0,1]of R, which of the following must be true?
1. X is compact 2.H is Hausdorff 3. X is connected
答案选择只有2 求大神解释。拓扑实在缺根筋
44 已经解决了
现在28还是不懂
求解答let A and B be subspaces of a vector space V. which of the following must be subspaces of V?
1. A+B={a+b:a属于A,b属于b} 2.A∪B 3. A∩B 4.{x属于V:x∉A}
答案选的是1和3