Basic Analysis I — Real Analysis · Problem 3.3.5

Continuous Functions — Jiri Lebl

Mathematics — Real Analysis · extreme-and-intermediate-value-theorems

Problem

Suppose g(x)g(x) is a monic polynomial of odd degree dd, that is, g(x)=xd+bd−1xd−1+⋯+b1x+b0,g(x) = x^d + b_{d-1}x^{d-1} + \cdots + b_1 x + b_0, for some real numbers b0,b1,…,bd−1b_0, b_1, \ldots, b_{d-1}. Show that there exists a K∈NK \in \mathbb{N} such that g(−K)<0g(-K) < 0. Hint: Make sure to use the fact that dd is odd. You will have to use that (−n)d=−(nd)(-n)^d = -(n^d).

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