If we need to calculate the derivative of a function at a point, there are two ways we can think about doing this. For example suppose f(x) = x2 - z, and we need to determine the value of f(4).
If we need to calculate the derivative of a function at a point, there are two ways we can think about doing this. For example suppose f(x) = x2 - z, and we need to determine the value of f(4).
Calculus: Early Transcendentals
8th Edition
ISBN:9781285741550
Author:James Stewart
Publisher:James Stewart
Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
Related questions
Topic Video
Question

Transcribed Image Text:If we need to calculate the derivative of a function at a point, there are two ways we can think about doing
this. For example suppose f() = x – x, and we need to determine the value of f(4).
One option is to just calculate the derivative at that point by plugging the point into the limit definition, like
this:
f(4 + h) – f(4)
(
(4 + h)² – (4 + h)) - (4² – 4)
f'(4) = lim
(16 + 8h + h2 -4 – h) - (16 - 4)
lim
7h + h2
= lim
h(7+ h)
lim
h
= lim
h→0
h
lim 7+h = 7.
||
h
h
h
Another option is to calculate f'(x) in terms of x, and then plug in a value for x at the end, like this:
f(x + h) – f(x)
(2+ h) – (x + h)) - (2² – a)
(22 + 2xh + h² – z – h) – (22 – 2)
lim
f'(x) = lim
= lim
2xh + h2 - h
h(2x + h - 1)
= lim
h 0
h
h
= lim
= lim
h
h
h
that is to say, f'(x)
= 2x – 1, and therefore f'(4) = 2(4) – 1 = 7.
Notice that we get the answer f'(4) = 7 both ways. The second approach might look somewhat more
complicated at first, but it turns out to be much more efficient if we ever need to know the value of the
derivative at multiple points. For example, if we now wanted to know f' (1), f'(7) and f'(11), we wouldn't
need to calculate the limit definitions all over again
formula f'(x) = 2x – 1.
-- we could just plug the numbers 1, 7 and 11 into the
Let g(x) = x – x².
g(3 + h) – g(3)
Find g'(3) by calculating lim
h-0
h
g(x + h) – g(x)
Next, find g'(æ) by calculating lim
h 0
h
Finally, find g'(3) by plugging 3 into g'(x).
Expert Solution

This question has been solved!
Explore an expertly crafted, step-by-step solution for a thorough understanding of key concepts.
Step by step
Solved in 3 steps

Knowledge Booster
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, calculus and related others by exploring similar questions and additional content below.Recommended textbooks for you

Calculus: Early Transcendentals
Calculus
ISBN:
9781285741550
Author:
James Stewart
Publisher:
Cengage Learning

Thomas' Calculus (14th Edition)
Calculus
ISBN:
9780134438986
Author:
Joel R. Hass, Christopher E. Heil, Maurice D. Weir
Publisher:
PEARSON

Calculus: Early Transcendentals (3rd Edition)
Calculus
ISBN:
9780134763644
Author:
William L. Briggs, Lyle Cochran, Bernard Gillett, Eric Schulz
Publisher:
PEARSON

Calculus: Early Transcendentals
Calculus
ISBN:
9781285741550
Author:
James Stewart
Publisher:
Cengage Learning

Thomas' Calculus (14th Edition)
Calculus
ISBN:
9780134438986
Author:
Joel R. Hass, Christopher E. Heil, Maurice D. Weir
Publisher:
PEARSON

Calculus: Early Transcendentals (3rd Edition)
Calculus
ISBN:
9780134763644
Author:
William L. Briggs, Lyle Cochran, Bernard Gillett, Eric Schulz
Publisher:
PEARSON

Calculus: Early Transcendentals
Calculus
ISBN:
9781319050740
Author:
Jon Rogawski, Colin Adams, Robert Franzosa
Publisher:
W. H. Freeman


Calculus: Early Transcendental Functions
Calculus
ISBN:
9781337552516
Author:
Ron Larson, Bruce H. Edwards
Publisher:
Cengage Learning