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Finding Limits: Properties of Limits

For the following exercises, find the limits if lim x c f ( x ) = −3 and lim x c g ( x ) = 5.

lim x c ( f ( x ) + g ( x ) )

2

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lim x c f ( x ) g ( x )

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lim x c ( f ( x ) g ( x ) )

−15

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lim x 0 + f ( x ) , f ( x ) = { 3 x 2 + 2 x + 1 5 x + 3    x > 0 x < 0

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lim x 0 f ( x ) , f ( x ) = { 3 x 2 + 2 x + 1 5 x + 3    x > 0 x < 0

3

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lim x 3 + ( 3 x 〚x〛 )

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For the following exercises, evaluate the limits using algebraic techniques.

lim h 0 ( ( h + 6 ) 2 36 h )

12

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lim x 25 ( x 2 625 x 5 )

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lim x 1 ( x 2 9 x x )

10

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lim x 4 7 12 x + 1 x 4

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

1 9

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Continuity

For the following exercises, use numerical evidence to determine whether the limit exists at x = a . If not, describe the behavior of the graph of the function at x = a .

f ( x ) = 2 x 4 ;   a = 4

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f ( x ) = 2 ( x 4 ) 2 ;   a = 4

At x = 4 , the function has a vertical asymptote.

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f ( x ) = x x 2 x 6 ;   a = 3

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f ( x ) = 6 x 2 + 23 x + 20 4 x 2 25 ;   a = 5 2

removable discontinuity at a = 5 2

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f ( x ) = x 3 9 x ;   a = 9

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For the following exercises, determine where the given function f ( x ) is continuous. Where it is not continuous, state which conditions fail, and classify any discontinuities.

f ( x ) = x 2 2 x 15

continuous on ( , )

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f ( x ) = x 2 2 x 15 x 5

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f ( x ) = x 2 2 x x 2 4 x + 4

removable discontinuity at x = 2. f ( 2 ) is not defined, but limits exist.

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f ( x ) = x 3 125 2 x 2 12 x + 10

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f ( x ) = x 2 1 x 2 x

discontinuity at x = 0 and x = 2. Both f ( 0 ) and f ( 2 ) are not defined.

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f ( x ) = x + 2 x 2 3 x 10

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f ( x ) = x + 2 x 3 + 8

removable discontinuity at x = 2.   f ( 2 ) is not defined.

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Derivatives

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

f ( x ) = ln ( x )

ln ( x + h ) ln ( x ) h

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For the following exercises, find the derivative of the function.

Find the equation of the tangent line to the graph of f ( x ) at the indicated x value.
f ( x ) = x 3 + 4 x ; x = 2.

y = 8 x + 16

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For the following exercises, with the aid of a graphing utility, explain why the function is not differentiable everywhere on its domain. Specify the points where the function is not differentiable.

Given that the volume of a right circular cone is V = 1 3 π r 2 h and that a given cone has a fixed height of 9 cm and variable radius length, find the instantaneous rate of change of volume with respect to radius length when the radius is 2 cm. Give an exact answer in terms of π

12 π

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Practice test

For the following exercises, use the graph of f in [link] .

Graph of a piecewise function with two segments. The first segment goes from negative infinity to (-1, 0), an open point, and the second segment goes from (-1, 3), an open point, to positive infinity.

lim x −1 + f ( x )

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lim x −1 f ( x )

0

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lim x −2 f ( x )

−1

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At what values of x is f discontinuous? What property of continuity is violated?

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For the following exercises, with the use of a graphing utility, use numerical or graphical evidence to determine the left- and right-hand limits of the function given as x approaches a . If the function has a limit as x approaches a , state it. If not, discuss why there is no limit

f ( x ) = { 1 x 3 ,  i f x 2 x 3 + 1 , i f x > 2    a = 2

lim x 2 f ( x ) = 5 2 a and lim x 2 + f ( x ) = 9 Thus, the limit of the function as x approaches 2 does not exist.

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f ( x ) = { x 3 + 1 , i f x < 1 3 x 2 1 , i f x = 1 x + 3 + 4 , i f x > 1    a = 1

For the following exercises, evaluate each limit using algebraic techniques.

lim x −5 ( 1 5 + 1 x 10 + 2 x )

1 50

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lim h 0 ( h 2 + 25 5 h 2 )

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lim h 0 ( 1 h 1 h 2 + h )

1

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For the following exercises, determine whether or not the given function f is continuous. If it is continuous, show why. If it is not continuous, state which conditions fail.

f ( x ) = x 3 4 x 2 9 x + 36 x 3 3 x 2 + 2 x 6

removable discontinuity at x = 3

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For the following exercises, use the definition of a derivative to find the derivative of the given function at x = a .

f ( x ) = 3 x

f ' ( x ) = 3 2 a 3 2

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For the graph in [link] , determine where the function is continuous/discontinuous and differentiable/not differentiable.

Graph of a piecewise function with three segments. The first segment goes from negative infinity to (-2, -1), an open point; the second segment goes from (-2, -4), an open point, to (0, 0), a closed point; the final segment goes from (0, 1), an open point, to positive infinity.

discontinuous at –2,0, not differentiable at –2,0, 2.

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For the following exercises, with the aid of a graphing utility, explain why the function is not differentiable everywhere on its domain. Specify the points where the function is not differentiable.

f ( x ) = | x 2 | | x + 2 |

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f ( x ) = 2 1 + e 2 x

not differentiable at x = 0 (no limit)

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For the following exercises, explain the notation in words when the height of a projectile in feet, s , is a function of time t in seconds after launch and is given by the function s ( t ) .

s ( 2 )

the height of the projectile at t = 2 seconds

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s ( 2 ) s ( 1 ) 2 1

the average velocity from t = 1  to  t = 2

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For the following exercises, use technology to evaluate the limit.

lim x 0 sin ( x ) 3 x

1 3

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lim x 0 tan 2 ( x ) 2 x

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lim x 0 sin ( x ) ( 1 cos ( x ) ) 2 x 2

0

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Evaluate the limit by hand.

lim x 1 f ( x ) ,  where   f ( x ) = { 4 x 7 x 1 x 2 4 x = 1

At what value(s) of x is the function below discontinuous?

f ( x ) = { 4 x 7 x 1 x 2 4 x = 1

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For the following exercises, consider the function whose graph appears in [link] .

Graph of a positive parabola.

Find the average rate of change of the function from x = 1  to  x = 3.

2

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Find all values of x at which f ' ( x ) = 0.

x = 1

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Find all values of x at which f ' ( x ) does not exist.

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Find an equation of the tangent line to the graph of f the indicated point: f ( x ) = 3 x 2 2 x 6 ,    x = 2

y = 14 x 18

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For the following exercises, use the function f ( x ) = x ( 1 x ) 2 5 .

Graph the function f ( x ) = x ( 1 x ) 2 5 by entering f ( x ) = x ( ( 1 x ) 2 ) 1 5 and then by entering f ( x ) = x ( ( 1 x ) 1 5 ) 2 .

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Explore the behavior of the graph of f ( x ) around x = 1 by graphing the function on the following domains, [0.9, 1.1], [0.99, 1.01], [0.999, 1.001], and [0.9999, 1.0001]. Use this information to determine whether the function appears to be differentiable at x = 1.

The graph is not differentiable at x = 1 (cusp).

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For the following exercises, find the derivative of each of the functions using the definition: lim h 0 f ( x + h ) f ( x ) h

f ( x ) = 4 x 2 7

f ' ( x ) = 8 x

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f ( x ) = 1 x + 2

f ' ( x ) = 1 ( 2 + x ) 2

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f ( x ) = x 3 + 1

f ' ( x ) = 3 x 2

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f ( x ) = x 1

f ' ( x ) = 1 2 x 1

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Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
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John Reply
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Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
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Maurice
answer
Magreth
progressive wave
Magreth
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hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
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Practice Key Terms 7

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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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