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Find all critical points for f ( x ) = x 3 1 2 x 2 2 x + 1 .

x = 2 3 , x = 1

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Locating absolute extrema

The extreme value theorem states that a continuous function over a closed, bounded interval has an absolute maximum and an absolute minimum. As shown in [link] , one or both of these absolute extrema could occur at an endpoint. If an absolute extremum does not occur at an endpoint, however, it must occur at an interior point, in which case the absolute extremum is a local extremum. Therefore, by [link] , the point c at which the local extremum occurs must be a critical point. We summarize this result in the following theorem.

Location of absolute extrema

Let f be a continuous function over a closed, bounded interval I . The absolute maximum of f over I and the absolute minimum of f over I must occur at endpoints of I or at critical points of f in I .

With this idea in mind, let’s examine a procedure for locating absolute extrema.

Problem-solving strategy: locating absolute extrema over a closed interval

Consider a continuous function f defined over the closed interval [ a , b ] .

  1. Evaluate f at the endpoints x = a and x = b .
  2. Find all critical points of f that lie over the interval ( a , b ) and evaluate f at those critical points.
  3. Compare all values found in (1) and (2). From [link] , the absolute extrema must occur at endpoints or critical points. Therefore, the largest of these values is the absolute maximum of f . The smallest of these values is the absolute minimum of f .

Now let’s look at how to use this strategy to find the absolute maximum and absolute minimum values for continuous functions.

Locating absolute extrema

For each of the following functions, find the absolute maximum and absolute minimum over the specified interval and state where those values occur.

  1. f ( x ) = x 2 + 3 x 2 over [ 1 , 3 ] .
  2. f ( x ) = x 2 3 x 2 / 3 over [ 0 , 2 ] .
  1. Step 1. Evaluate f at the endpoints x = 1 and x = 3 .
    f ( 1 ) = 0 and f ( 3 ) = −2

    Step 2. Since f ( x ) = −2 x + 3 , f is defined for all real numbers x . Therefore, there are no critical points where the derivative is undefined. It remains to check where f ( x ) = 0 . Since f ( x ) = −2 x + 3 = 0 at x = 3 2 and 3 2 is in the interval [ 1 , 3 ] , f ( 3 2 ) is a candidate for an absolute extremum of f over [ 1 , 3 ] . We evaluate f ( 3 2 ) and find
    f ( 3 2 ) = 1 4 .

    Step 3. We set up the following table to compare the values found in steps 1 and 2.
    x f ( x ) Conclusion
    0 0
    3 2 1 4 Absolute maximum
    3 −2 Absolute minimum

    From the table, we find that the absolute maximum of f over the interval [1, 3] is 1 4 , and it occurs at x = 3 2 . The absolute minimum of f over the interval [1, 3] is −2 , and it occurs at x = 3 as shown in the following graph.
    The function f(x) = – x2 + 3x – 2 is graphed from (1, 0) to (3, −2), with its maximum marked at (3/2, 1/4).
    This function has both an absolute maximum and an absolute minimum.
  2. Step 1. Evaluate f at the endpoints x = 0 and x = 2 .
    f ( 0 ) = 0 and f ( 2 ) = 4 3 4 3 0.762

    Step 2. The derivative of f is given by
    f ( x ) = 2 x 2 x 1 / 3 = 2 x 4 / 3 2 x 1 / 3

    for x 0 . The derivative is zero when 2 x 4 / 3 2 = 0 , which implies x = ± 1 . The derivative is undefined at x = 0 . Therefore, the critical points of f are x = 0 , 1 , −1 . The point x = 0 is an endpoint, so we already evaluated f ( 0 ) in step 1. The point x = −1 is not in the interval of interest, so we need only evaluate f ( 1 ) . We find that
    f ( 1 ) = −2 .

    Step 3. We compare the values found in steps 1 and 2, in the following table.
    x f ( x ) Conclusion
    0 0 Absolute maximum
    1 −2 Absolute minimum
    2 −0.762

    We conclude that the absolute maximum of f over the interval [0, 2] is zero, and it occurs at x = 0 . The absolute minimum is −2, and it occurs at x = 1 as shown in the following graph.
    The function f(x) = x2 – 3x2/3 is graphed from (0, 0) to (2, −0.762), with its minimum marked at (1, −2).
    This function has an absolute maximum at an endpoint of the interval.
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Questions & Answers

Three charges q_{1}=+3\mu C, q_{2}=+6\mu C and q_{3}=+8\mu C are located at (2,0)m (0,0)m and (0,3) coordinates respectively. Find the magnitude and direction acted upon q_{2} by the two other charges.Draw the correct graphical illustration of the problem above showing the direction of all forces.
Kate Reply
To solve this problem, we need to first find the net force acting on charge q_{2}. The magnitude of the force exerted by q_{1} on q_{2} is given by F=\frac{kq_{1}q_{2}}{r^{2}} where k is the Coulomb constant, q_{1} and q_{2} are the charges of the particles, and r is the distance between them.
Muhammed
What is the direction and net electric force on q_{1}= 5µC located at (0,4)r due to charges q_{2}=7mu located at (0,0)m and q_{3}=3\mu C located at (4,0)m?
Kate Reply
what is the change in momentum of a body?
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what is a capacitor?
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Capacitor is a separation of opposite charges using an insulator of very small dimension between them. Capacitor is used for allowing an AC (alternating current) to pass while a DC (direct current) is blocked.
Gautam
A motor travelling at 72km/m on sighting a stop sign applying the breaks such that under constant deaccelerate in the meters of 50 metres what is the magnitude of the accelerate
Maria Reply
please solve
Sharon
8m/s²
Aishat
What is Thermodynamics
Muordit
velocity can be 72 km/h in question. 72 km/h=20 m/s, v^2=2.a.x , 20^2=2.a.50, a=4 m/s^2.
Mehmet
A boat travels due east at a speed of 40meter per seconds across a river flowing due south at 30meter per seconds. what is the resultant speed of the boat
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50 m/s due south east
Someone
which has a higher temperature, 1cup of boiling water or 1teapot of boiling water which can transfer more heat 1cup of boiling water or 1 teapot of boiling water explain your . answer
Ramon Reply
I believe temperature being an intensive property does not change for any amount of boiling water whereas heat being an extensive property changes with amount/size of the system.
Someone
Scratch that
Someone
temperature for any amount of water to boil at ntp is 100⁰C (it is a state function and and intensive property) and it depends both will give same amount of heat because the surface available for heat transfer is greater in case of the kettle as well as the heat stored in it but if you talk.....
Someone
about the amount of heat stored in the system then in that case since the mass of water in the kettle is greater so more energy is required to raise the temperature b/c more molecules of water are present in the kettle
Someone
definitely of physics
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physics, biology and chemistry this is my Field
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field is a region of space under the influence of some physical properties
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what is ogarnic chemistry
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determine the slope giving that 3y+ 2x-14=0
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Another formula for Acceleration
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a=v/t. a=f/m a
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pratica A on solution of hydro chloric acid,B is a solution containing 0.5000 mole ofsodium chlorid per dm³,put A in the burret and titrate 20.00 or 25.00cm³ portion of B using melting orange as the indicator. record the deside of your burret tabulate the burret reading and calculate the average volume of acid used?
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Two bodies attract each other electrically. Do they both have to be charged? Answer the same question if the bodies repel one another.
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No. According to Isac Newtons law. this two bodies maybe you and the wall beside you. Attracting depends on the mass och each body and distance between them.
Dlovan
Are you really asking if two bodies have to be charged to be influenced by Coulombs Law?
Robert
like charges repel while unlike charges atttact
Raymond
What is specific heat capacity
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Specific heat capacity is a measure of the amount of energy required to raise the temperature of a substance by one degree Celsius (or Kelvin). It is measured in Joules per kilogram per degree Celsius (J/kg°C).
AI-Robot
specific heat capacity is the amount of energy needed to raise the temperature of a substance by one degree Celsius or kelvin
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Source:  OpenStax, Calculus volume 1. OpenStax CNX. Feb 05, 2016 Download for free at http://cnx.org/content/col11964/1.2
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