/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Q. 91 Prove part (b) of Theorem 3.8: W... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

Prove part (b) of Theorem 3.8: With hypotheses as stated in the theorem, if x=c is a critical point of f, where f'(x)<0 to the left of c and f'(x)>0 to the right of c, then f has a local minimum at x=c.

Short Answer

Expert verified

The part(b) of theorem3.8 is proved.

Step by step solution

01

Step 1. Given Information 

We are given a function f and theorem 3.8.

02

Step 2. Proving the statement 

Suppose f'(x)<0for x∈(a,c)and f'(x)>0for x∈(c,b), that is suppose f is decreasing on (a,c]and increasing on [c,b). We will show that f(c)≤f(x)for all x∈(a,b) which will tell us that f has local minimum at x=c.

Given that x∈(a,b), there will be 3cases to consider.

First if x=cthen clearly f(c)=f(x).

Second if a<x<c then since f is decreasing on (a,c]we have f(x)>f(c).

Third if c<x<b then since f is increasing on [c,b), we have f(x)>f(c).

In all the three cases we have f(x)≥f(c) and therefore f has a local minimum at x=c.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Study anywhere. Anytime. Across all devices.