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Advanced Engineering Mathematics
10th Edition
ISBN: 9780470458365
Author: Erwin Kreyszig
Publisher: Wiley, John & Sons, Incorporated
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![Let \( I := [a, b] \) and let \( f: I \rightarrow \mathbb{R} \) be a continuous function such that \( f(x) > 0 \) for each \( x \) in \( I \). Prove that there exists a number \( \alpha > 0 \) such that \( f(x) \geq \alpha \) for all \( x \in I \).](https://content.bartleby.com/qna-images/question/e57a7d70-87de-4a1f-8104-5b2578062c6c/bbec444b-b0ed-49b1-a831-eda05bb65ec7/7aji92a_thumbnail.jpeg)
Transcribed Image Text:Let \( I := [a, b] \) and let \( f: I \rightarrow \mathbb{R} \) be a continuous function such that \( f(x) > 0 \) for each \( x \) in \( I \). Prove that there exists a number \( \alpha > 0 \) such that \( f(x) \geq \alpha \) for all \( x \in I \).
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- 2. Is the proof correct? Either state that it is, or circle the first error and explain what is incorrect about it. If the proof is not correct, can it be fixed to prove the claim true? Claim: If f : (0,1] → R and g : [1,2) → R are uniformly continuous on their domains, and f(1) = g(1), then the function h : (0, 2) → R, defined by h(æ) = { F(x) for x € (0, 1] | 9(x) for x e [1, 2) is uniformly continuous on (0, 2). Proof: Let e > 0. Since f is uniformly continuous on (0, 1], there exists d1 > 0 such that if x, y E (0, 1] and |æ – y| 0 such that if æ, y E [1, 2) and |r – y| < d2, then |9(x) – 9(y)| < €/2. Let 8 = min{d1, &2}. Now suppose r, Y E (0, 2) with x < y and |x – y| < 8. If x, y E (0, 1], then |x – y| < 8 < 81 and so |h(x) – h(y)| = |f (x) – f(y)|< e/2 < e. If x, y € (1,2), then |æ – y| < 8 < d2 and so |h(x) – h(y)| = |9(x) – g(y)| < e/2 < e. If x € (0,1) and y E (1,2), then |x – 1| < |x – y| < 8 < dị and |1 – y| < |æ – y| < 8 < 82 so that |h(x) – h(y)| = |f (x) – f(1) + g(1) –…arrow_forward2. Let f: I R be a continuous function on a bounded, closed interval I= [a, b). Show that f has a minimum on I.arrow_forwardUse the Mean Value Theorem to prove: If f(x) and g(x) are differentiable on an interval (a, b) and f'(x) = g'(x) for all x in (a, b), then there is a constant k such that g(x) = f(x) + c for all x in (a, b).arrow_forward
- Define f(0,0) in a way that extends f to be continuous at the origin. x²y² 2y in [2x² -221 +22²) x² + X f(x,y) = In Let f(0,0) be defined to be (Type an exact answer.)arrow_forwardLet f : R → R be a continuous function satisfying f(x + y) = f (x) · fV) for all x, y E R 1. Show that either f (x) = 0 for all x ER or f(x) > 0 for all x E R 2. Using part 1, show that either = 0 for all x ER or there exists a > 0 such that f (x) = a* for all x ERarrow_forward
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