
PreCalculus PreCalculus Math Forum 
 LinkBack  Thread Tools  Display Modes 
February 21st, 2018, 01:23 PM  #1 
Newbie Joined: Feb 2018 From: San Jose, CA Posts: 1 Thanks: 0  First Post... Continuity of Piecewise func
I know this is probably pretty basic, but just started in Calculus. Any help would be appreciated. I know the limit from the left is 3, and the limit from the right is 3, and the f(1)=4 which makes is discontinuous. Not sure how to format the interval to make it continuous.

February 21st, 2018, 01:54 PM  #2 
Global Moderator Joined: Dec 2006 Posts: 20,098 Thanks: 1905 
Moved to PreCalculus. The function is undefined at x = 0 (or 2 if the denominator was intended to be x+2) and discontinuous at x = 1. What notation for intervals have you been taught? Last edited by skipjack; February 21st, 2018 at 04:53 PM. Reason: to correct, as I'd misread the image 
February 21st, 2018, 04:36 PM  #3 
Math Team Joined: Jan 2015 From: Alabama Posts: 3,261 Thanks: 895 
The function I see (perhaps it has been changed?) is f(x)= 9/(x+ 2) if x< 1 (you wrote "9/x+ 2" but I think that 9/(x+ 2) was intended) f(x)= 4 if x= 1 and f(x)= 5x 2 if x> 1 The limit at 1 "from the left" is the limit of 9/(x+ 2). That function is continuous at x= 1 so the limit is 9/(1+ 2)= 9/3= 3. The limit "from the right" is the limit of 5x 2. That function is continuous at x= 1 so the limit is 5(1) 2= 3. That is enough to say that "the limit" is 3. But the value of the function is 4 at x= 1 so, even though the limit exists, the function is NOT continuous at x= 1. 
February 21st, 2018, 07:32 PM  #4 
Senior Member Joined: May 2016 From: USA Posts: 1,250 Thanks: 516 
I suspect that the question is misstated. I suspect the real question is how to define the function to make it continuous at x = 1.

February 22nd, 2018, 09:00 AM  #5  
Math Team Joined: Jan 2015 From: Alabama Posts: 3,261 Thanks: 895  Quote:
 

Tags 
continuity, func, piecewise, post 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
continuity problem with piecewise function?  Leesasomething  Calculus  2  April 21st, 2011 12:30 AM 
how do you know if a func is Differentiable?  peaceofmind  Calculus  12  April 19th, 2011 01:09 AM 
Der. of a Inverse Trig. Func. Help  Ibanez  Calculus  2  April 13th, 2009 04:45 AM 
Help with cos+func = 1/1  Jazzmazz  Algebra  2  December 16th, 2007 01:17 PM 
how do you know if a func is Differentiable?  peaceofmind  Algebra  12  December 31st, 1969 04:00 PM 