Simple Precalculus: Average rate of change

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SUMMARY

The discussion centers on calculating the average rate of change for the function g(x) = 1/x between x = 1 and x = a. The formula used is (f(b) - f(a)) / (b - a), leading to the expression ((1/a) - 1) / (a - 1). The correct answer is confirmed to be -(1/a) after simplifying the expression by factoring out -1 from the numerator. The participant acknowledges an oversight in their calculations, emphasizing the importance of basic algebraic manipulation in solving such problems.

PREREQUISITES
  • Understanding of functions and their properties, specifically rational functions.
  • Familiarity with the concept of average rate of change in calculus.
  • Basic algebra skills, including factoring and simplifying expressions.
  • Knowledge of the function notation and evaluation.
NEXT STEPS
  • Study the concept of limits and how they relate to average rates of change.
  • Learn about derivatives and their application in finding instantaneous rates of change.
  • Practice more problems involving average rates of change for various functions.
  • Explore the implications of rational functions in calculus, particularly in relation to asymptotes.
USEFUL FOR

Students studying precalculus or calculus, educators teaching these concepts, and anyone seeking to improve their algebraic manipulation skills in mathematical problem-solving.

DarrenM
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Homework Statement


Find the average rate of change:
g(x)=1/x; x = 1, x = a


Homework Equations


(f(b)-f(a))/(b-a) = Average rate of change


The Attempt at a Solution


I've spent far too much time on this problem, but I know I'm making a stupid error and I just can't pin it down. So far, the steps I'm pretty confident about:

g(1) = 1/1 = 1
g(a) = 1/a

Average rate of change = ((1/a)-1)/(a-1)

According to the book the answer is -(1/a)... but I'm just not seeing it.
 
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1/a-1 = (1-a)/a :wink:
 
Yea, got it now. It was just as ridiculous an oversight as I had originally thought. I kept getting to the point in the problem where I had (1-a)/(a(a-1)) and going, "Oh, I can't divide those binomials!" Factor out a -1 from the numerator, cancel out the resulting binomial with the denominator and there's the answer... staring me right in the face. I'm rather embarrassed that I had so much trouble with such a simple problem, and that I forgot such a basic rule. Thanks for the help.
 

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