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Determine where the function f ( x ) = { π x 4 ,    x < 2 π x ,      2 x 6 2 π x ,    x > 6 is discontinuous.

x = 6

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Determining whether a function is continuous

To determine whether a piecewise function    is continuous or discontinuous, in addition to checking the boundary points, we must also check whether each of the functions that make up the piecewise function is continuous.

Given a piecewise function, determine whether it is continuous.

  1. Determine whether each component function of the piecewise function is continuous. If there are discontinuities, do they occur within the domain where that component function is applied?
  2. For each boundary point x = a of the piecewise function, determine if each of the three conditions hold.

Determining whether a piecewise function is continuous

Determine whether the function below is continuous. If it is not, state the location and type of each discontinuity.

f x = { sin ( x ) , x < 0 x 3 , x > 0

The two functions composing this piecewise function are f ( x ) = sin ( x ) on x < 0 and f ( x ) = x 3 on x > 0. The sine function and all polynomial functions are continuous everywhere. Any discontinuities would be at the boundary point,

At x = 0 , let us check the three conditions of continuity.

Condition 1:

f ( 0 )  does not exist . Condition 1 fails .

Because all three conditions are not satisfied at x = 0 , the function f ( x ) is discontinuous at x = 0.

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Access these online resources for additional instruction and practice with continuity.

Key concepts

  • A continuous function can be represented by a graph without holes or breaks.
  • A function whose graph has holes is a discontinuous function.
  • A function is continuous at a particular number if three conditions are met:
    • Condition 1: f ( a ) exists.
    • Condition 2: lim x a f ( x ) exists at x = a .
    • Condition 3: lim x a f ( x ) = f ( a ) .
  • A function has a jump discontinuity if the left- and right-hand limits are different, causing the graph to “jump.”
  • A function has a removable discontinuity if it can be redefined at its discontinuous point to make it continuous. See [link] .
  • Some functions, such as polynomial functions, are continuous everywhere. Other functions, such as logarithmic functions, are continuous on their domain. See [link] and [link] .
  • For a piecewise function to be continuous each piece must be continuous on its part of the domain and the function as a whole must be continuous at the boundaries. See [link] and [link] .

Section exercises

Verbal

State in your own words what it means for a function f to be continuous at x = c .

Informally, if a function is continuous at x = c , then there is no break in the graph of the function at f ( c ) , and f ( c ) is defined.

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State in your own words what it means for a function to be continuous on the interval ( a , b ) .

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Algebraic

For the following exercises, determine why the function f is discontinuous at a given point a on the graph. State which condition fails.

f ( x ) = ln   |   x + 3   | , a = 3

discontinuous at a = 3 ; f ( 3 ) does not exist

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f ( x ) = ln   |   5 x 2   | , a = 2 5

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f ( x ) = x 2 16 x + 4 , a = 4

removable discontinuity at a = 4 ; f ( 4 ) is not defined

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f ( x ) = x 2 16 x x , a = 0

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f ( x ) = { x ,     x 3 2 x , x = 3   a = 3

Discontinuous at a = 3 ; lim x 3 f ( x ) = 3 , but f ( 3 ) = 6 , which is not equal to the limit.

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Questions & Answers

how did you get 1640
Noor Reply
If auger is pair are the roots of equation x2+5x-3=0
Peter Reply
Wayne and Dennis like to ride the bike path from Riverside Park to the beach. Dennis’s speed is seven miles per hour faster than Wayne’s speed, so it takes Wayne 2 hours to ride to the beach while it takes Dennis 1.5 hours for the ride. Find the speed of both bikers.
MATTHEW Reply
420
Sharon
from theory: distance [miles] = speed [mph] × time [hours] info #1 speed_Dennis × 1.5 = speed_Wayne × 2 => speed_Wayne = 0.75 × speed_Dennis (i) info #2 speed_Dennis = speed_Wayne + 7 [mph] (ii) use (i) in (ii) => [...] speed_Dennis = 28 mph speed_Wayne = 21 mph
George
Let W be Wayne's speed in miles per hour and D be Dennis's speed in miles per hour. We know that W + 7 = D and W * 2 = D * 1.5. Substituting the first equation into the second: W * 2 = (W + 7) * 1.5 W * 2 = W * 1.5 + 7 * 1.5 0.5 * W = 7 * 1.5 W = 7 * 3 or 21 W is 21 D = W + 7 D = 21 + 7 D = 28
Salma
Devon is 32 32​​ years older than his son, Milan. The sum of both their ages is 54 54​. Using the variables d d​ and m m​ to represent the ages of Devon and Milan, respectively, write a system of equations to describe this situation. Enter the equations below, separated by a comma.
Aaron Reply
find product (-6m+6) ( 3m²+4m-3)
SIMRAN Reply
-42m²+60m-18
Salma
what is the solution
bill
how did you arrive at this answer?
bill
-24m+3+3mÁ^2
Susan
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Amira
I only got 42 the rest i don't know how to solve it. Please i need help from anyone to help me improve my solving mathematics please
Amira
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Aphelele
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Bajemah
-6m(3mA²+4m-3)+6(3mA²+4m-3) =-18m²A²-24m²+18m+18mA²+24m-18 Rearrange like items -18m²A²-24m²+42m+18A²-18
Salma
complete the table of valuesfor each given equatio then graph. 1.x+2y=3
Jovelyn Reply
x=3-2y
Salma
y=x+3/2
Salma
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Enock
given that (7x-5):(2+4x)=8:7find the value of x
Nandala
3x-12y=18
Kelvin
please why isn't that the 0is in ten thousand place
Grace Reply
please why is it that the 0is in the place of ten thousand
Grace
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A meditation garden is in the shape of a right triangle, with one leg 7 feet. The length of the hypotenuse is one more than the length of one of the other legs. Find the lengths of the hypotenuse and the other leg
Marry Reply
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Enock
state in which quadrant or on which axis each of the following angles given measure. in standard position would lie 89°
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Method
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Enock
what the last part of the problem mean?
Roger
The Jones family took a 15 mile canoe ride down the Indian River in three hours. After lunch, the return trip back up the river took five hours. Find the rate, in mph, of the canoe in still water and the rate of the current.
cameron Reply
Shakir works at a computer store. His weekly pay will be either a fixed amount, $925, or $500 plus 12% of his total sales. How much should his total sales be for his variable pay option to exceed the fixed amount of $925.
mahnoor Reply
I'm guessing, but it's somewhere around $4335.00 I think
Lewis
12% of sales will need to exceed 925 - 500, or 425 to exceed fixed amount option. What amount of sales does that equal? 425 ÷ (12÷100) = 3541.67. So the answer is sales greater than 3541.67. Check: Sales = 3542 Commission 12%=425.04 Pay = 500 + 425.04 = 925.04. 925.04 > 925.00
Munster
difference between rational and irrational numbers
Arundhati Reply
When traveling to Great Britain, Bethany exchanged $602 US dollars into £515 British pounds. How many pounds did she receive for each US dollar?
Jakoiya Reply
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Solomon Reply
Jazmine trained for 3 hours on Saturday. She ran 8 miles and then biked 24 miles. Her biking speed is 4 mph faster than her running speed. What is her running speed?
Zack Reply
d=r×t the equation would be 8/r+24/r+4=3 worked out
Sheirtina
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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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