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Access the following online resource for additional instruction and practice with properties of limits.

Key concepts

  • The properties of limits can be used to perform operations on the limits of functions rather than the functions themselves. See [link] .
  • The limit of a polynomial function can be found by finding the sum of the limits of the individual terms. See [link] and [link] .
  • The limit of a function that has been raised to a power equals the same power of the limit of the function. Another method is direct substitution. See [link] .
  • The limit of the root of a function equals the corresponding root of the limit of the function.
  • One way to find the limit of a function expressed as a quotient is to write the quotient in factored form and simplify. See [link] .
  • Another method of finding the limit of a complex fraction is to find the LCD. See [link] .
  • A limit containing a function containing a root may be evaluated using a conjugate. See [link] .
  • The limits of some functions expressed as quotients can be found by factoring. See [link] .
  • One way to evaluate the limit of a quotient containing absolute values is by using numeric evidence. Setting it up piecewise can also be useful. See [link] .

Section exercises

Verbal

Give an example of a type of function f whose limit, as x approaches a , is f ( a ) .

If f is a polynomial function, the limit of a polynomial function as x approaches a will always be f ( a ) .

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When direct substitution is used to evaluate the limit of a rational function as x approaches a and the result is f ( a ) = 0 0 , does this mean that the limit of f does not exist?

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What does it mean to say the limit of f ( x ) , as x approaches c , is undefined?

It could mean either (1) the values of the function increase or decrease without bound as x approaches c , or (2) the left and right-hand limits are not equal.

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Algebraic

For the following exercises, evaluate the limits algebraically.

lim x 2 ( 5 x x 2 1 )

10 3

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lim x 2 ( x 2 5 x + 6 x + 2 )

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lim x 3 ( x 2 9 x 3 )

6

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lim x 1 ( x 2 2 x 3 x + 1 )

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lim x 3 2 ( 6 x 2 17 x + 12 2 x 3 )

1 2

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lim x 7 2 ( 8 x 2 + 18 x 35 2 x + 7 )

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lim x 3 ( x 2 9 x 5 x + 6 )

6

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lim x 3 ( 7 x 4 21 x 3 12 x 4 + 108 x 2 )

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lim x 3 ( x 2 + 2 x 3 x 3 )

does not exist

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lim h 0 ( ( 3 + h ) 3 27 h )

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lim h 0 ( ( 2 h ) 3 8 h )

12

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lim h 0 ( ( h + 3 ) 2 9 h )

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lim h 0 ( 5 h 5 h )

5 10

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lim x 0 ( 3 x 3 x )

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lim x 9 ( x 2 81 3 x )

108

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lim x 1 ( x x 2 1 x )

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lim x 0 ( x 1 + 2 x 1 )

1

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lim x 1 2 ( x 2 1 4 2 x 1 )

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lim x 4 ( x 3 64 x 2 16 )

6

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lim x 2 ( | x 2 | x 2 )

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lim x 2 + ( | x 2 | x 2 )

1

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lim x 2 ( | x 2 | x 2 )

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lim x 4 ( | x 4 | 4 x )

1

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lim x 4 + ( | x 4 | 4 x )

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lim x 4 ( | x 4 | 4 x )

does not exist

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lim x 2 ( 8 + 6 x x 2 x 2 )

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For the following exercise, use the given information to evaluate the limits: lim x c f ( x ) = 3 , lim x c g ( x ) = 5

lim x c [ 2 f ( x ) + g ( x ) ]

6 + 5

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lim x c [ 3 f ( x ) + g ( x ) ]

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lim x c f ( x ) g ( x )

3 5

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For the following exercises, evaluate the following limits.

lim x 2 cos ( π x )

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lim x 2 sin ( π x )

0

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lim x 2 sin ( π x )

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f ( x ) = { 2 x 2 + 2 x + 1 , x 0 x 3 ,   x > 0 lim x 0 + f ( x )

3

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f ( x ) = { 2 x 2 + 2 x + 1 , x 0 x 3 ,   x > 0 lim x 0 f ( x )

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f ( x ) = { 2 x 2 + 2 x + 1 , x 0 x 3 ,   x > 0 lim x 0 f ( x )

does not exist; right-hand limit is not the same as the left-hand limit.

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lim x 4 x + 5 3 x 4

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lim x 2 + ( 2 x 〚x〛 )

2

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lim x 2 x + 7 3 x 2 x 2

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lim x 3 + x 2 x 2 9

Limit does not exist; limit approaches infinity.

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For the following exercises, find the average rate of change f ( x + h ) f ( x ) h .

f ( x ) = 2 x 2 1

4 x + 2 h

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f ( x ) = x 2 + 4 x 100

2 x + h + 4

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f ( x ) = cos ( x )

cos ( x + h ) cos ( x ) h

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f ( x ) = 1 x

1 x ( x + h )

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f ( x ) = x

1 x + h + x

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Graphical

Find an equation that could be represented by [link] .

Graph of increasing function with a removable discontinuity at (2, 3).
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Find an equation that could be represented by [link] .

Graph of increasing function with a removable discontinuity at (-3, -1).

f ( x ) = x 2 + 5 x + 6 x + 3

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For the following exercises, refer to [link] .

Graph of increasing function from zero to positive infinity.

What is the right-hand limit of the function as x approaches 0?

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What is the left-hand limit of the function as x approaches 0?

does not exist

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Real-world applications

The position function s ( t ) = 16 t 2 + 144 t gives the position of a projectile as a function of time. Find the average velocity (average rate of change) on the interval [ 1 , 2 ] .

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The height of a projectile is given by s ( t ) = 64 t 2 + 192 t Find the average rate of change of the height from t = 1 second to t = 1.5 seconds.

52

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The amount of money in an account after t years compounded continuously at 4.25% interest is given by the formula A = A 0 e 0.0425 t , where A 0 is the initial amount invested. Find the average rate of change of the balance of the account from t = 1 year to t = 2 years if the initial amount invested is $1,000.00.

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Questions & Answers

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Why is unemployment rate never zero at full employment?
Priyanka Reply
bcoz of existence of frictional unemployment in our economy.
Umashankar
what is flexible exchang rate?
poudel
due to existence of the pple with disabilities
Abdulraufu
the demand of a good rises, causing the demand for another good to fall
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is it possible to leave every good at the same level
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Anuolu
is not really possible to let the value of a goods to be same at the same time.....
Salome
Suppose the inflation rate is 6%, does it mean that all the goods you purchase will cost 6% more than previous year? Provide with reasoning.
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Not necessarily. To measure the inflation rate economists normally use an averaged price index of a basket of certain goods. So if you purchase goods included in the basket, you will notice that you pay 6% more, otherwise not necessarily.
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Criteria for determining money supply
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Aggregate demand
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Source:  OpenStax, Precalculus. OpenStax CNX. Jan 19, 2016 Download for free at https://legacy.cnx.org/content/col11667/1.6
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