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Finding increasing and decreasing intervals on a graph

Given the function p ( t ) in [link] , identify the intervals on which the function appears to be increasing.

Graph of a polynomial.

We see that the function is not constant on any interval. The function is increasing where it slants upward as we move to the right and decreasing where it slants downward as we move to the right. The function appears to be increasing from t = 1 to t = 3 and from t = 4 on.

In interval notation    , we would say the function appears to be increasing on the interval (1,3) and the interval ( 4 , ) .

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Finding local extrema from a graph

Graph the function f ( x ) = 2 x + x 3 . Then use the graph to estimate the local extrema of the function and to determine the intervals on which the function is increasing.

Using technology, we find that the graph of the function looks like that in [link] . It appears there is a low point, or local minimum, between x = 2 and x = 3 , and a mirror-image high point, or local maximum, somewhere between x = −3 and x = −2.

Graph of a reciprocal function.
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Graph the function f ( x ) = x 3 6 x 2 15 x + 20 to estimate the local extrema of the function. Use these to determine the intervals on which the function is increasing and decreasing.

The local maximum appears to occur at ( 1 , 28 ) , and the local minimum occurs at ( 5 , 80 ) . The function is increasing on ( , 1 ) ( 5 , ) and decreasing on ( 1 , 5 ) .

Graph of a polynomial with a local maximum at (-1, 28) and local minimum at (5, -80).
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Finding local maxima and minima from a graph

For the function f whose graph is shown in [link] , find all local maxima and minima.

Graph of a polynomial.

Observe the graph of f . The graph attains a local maximum at x = 1 because it is the highest point in an open interval around x = 1. The local maximum is the y -coordinate at x = 1 , which is 2.

The graph attains a local minimum at   x = −1   because it is the lowest point in an open interval around x = −1. The local minimum is the y -coordinate at x = −1 , which is −2.

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Analyzing the toolkit functions for increasing or decreasing intervals

We will now return to our toolkit functions and discuss their graphical behavior in [link] , [link] , and [link] .

Table showing the increasing and decreasing intervals of the toolkit functions.
Table showing the increasing and decreasing intervals of the toolkit functions.
Table showing the increasing and decreasing intervals of the toolkit functions.

Use a graph to locate the absolute maximum and absolute minimum

There is a difference between locating the highest and lowest points on a graph in a region around an open interval (locally) and locating the highest and lowest points on the graph for the entire domain. The y - coordinates (output) at the highest and lowest points are called the absolute maximum and absolute minimum , respectively.

To locate absolute maxima and minima from a graph, we need to observe the graph to determine where the graph attains it highest and lowest points on the domain of the function. See [link] .

Graph of a segment of a parabola with an absolute minimum at (0, -2) and absolute maximum at (2, 2).

Not every function has an absolute maximum or minimum value. The toolkit function f ( x ) = x 3 is one such function.

Absolute maxima and minima

The absolute maximum    of f at x = c is f ( c ) where f ( c ) f ( x ) for all x in the domain of f .

The absolute minimum    of f at x = d is f ( d ) where f ( d ) f ( x ) for all x in the domain of f .

Finding absolute maxima and minima from a graph

For the function f shown in [link] , find all absolute maxima and minima.

Graph of a polynomial.

Observe the graph of f . The graph attains an absolute maximum in two locations, x = −2 and x = 2 , because at these locations, the graph attains its highest point on the domain of the function. The absolute maximum is the y -coordinate at x = −2 and x = 2 , which is 16.

The graph attains an absolute minimum at x = 3 , because it is the lowest point on the domain of the function’s graph. The absolute minimum is the y -coordinate at x = 3 , which is −10.

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Questions & Answers

how does the planets on our solar system orbit
cheten Reply
how many Messier objects are there in space
satish Reply
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Richard Reply
what are astronomy
Issan Reply
Astronomy (from Ancient Greek ἀστρονομία (astronomía) 'science that studies the laws of the stars') is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution.
Rafael
vjuvu
Elgoog
what is big bang theory?
Rosemary
what type of activity astronomer do?
Rosemary
No
Richard
the big bang theory is a theory which states that all matter was compressed together in one place the matter got so unstable it exploded releasing All its contents in the form of hydrogen
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I want to be an astronomer. That's my dream
Astrit
Who named the the whole galaxy?
Shola Reply
solar Univers
GPOWER
what is space
Richard
what is the dark matter
Richard
what are the factors upon which the atmosphere is stratified
Nicholas Reply
is the big bang the sun
Folakemi Reply
no
Sokak
bigbang is the beginning of the universe
Sokak
but thats just a theory
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nothing will happen, don't worry brother.
Vansh
what does comet means
GANGAIN Reply
these are Rocky substances between mars and jupiter
GANGAIN
Comets are cosmic snowballs of frozen gases , rock and dust that orbit the sun. They are mostly found between the orbits of Venus and Mercury.
Aarya
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John
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John
r u there
John
hey can anyone guide me abt international astronomy olympiad
sahil
how can we learn right and true ?
Govinda Reply
why the moon is always appear in an elliptical shape
Gatjuol Reply
Because when astroid hit the Earth then a piece of elliptical shape of the earth was separated which is now called moon.
Hemen
what's see level?
lidiya Reply
Did you mean eye sight or sea level
Minal
oh sorry it's sea level
lidiya
according to the theory of astronomers why the moon is always appear in an elliptical orbit?
Gatjuol
hi !!! I am new in astronomy.... I have so many questions in mind .... all of scientists of the word they just give opinion only. but they never think true or false ... i respect all of them... I believes whole universe depending on true ...থিউরি
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Elyana
we're all stars and galaxies a part of sun. how can science prove thx with respect old ancient times picture or books..or anything with respect to present time .but we r a part of that universe
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Michele
another theory of universe except big ban
Albash Reply
how was universe born
Asmit Reply
there many theory to born universe but what is the reality of big bang theory to born universe
Asmit
what is the exact value of π?
Nagalakshmi
by big bang
universal
there are many theories regarding this it's on you believe any theory that you think is true ex. eternal inflation theory, oscillation model theory, multiple universe theory the big bang theory etc.
Aarya
I think after Big Bang!
Michele
from where on earth could u observe all the stars during the during the course of an year
Karuna Reply
I think it couldn't possible on earth
Nagalakshmi
in this time i don't Know
Michele
is that so. the question was in the end of this chapter
Karuna
in theory, you could see them all from the equator (though over the course of a year, not at pne time). stars are measured in "declination", which is how far N or S of the equator (90* to -90*). Polaris is the North star, and is ALMOST 90* (+89*). So it would just barely creep over the horizon.
Christopher
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Source:  OpenStax, Algebra and trigonometry. OpenStax CNX. Nov 14, 2016 Download for free at https://legacy.cnx.org/content/col11758/1.6
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