July 25th, 2019, 07:02 AM  #1 
Newbie Joined: Nov 2018 From: Iran Posts: 12 Thanks: 0 Math Focus: calculus  double integral
Hello ,anyone got an idea about getting the area of the place surrounded by y=x^2+x and y=x by double integrals . really thanks by the way 
July 25th, 2019, 07:29 AM  #2 
Senior Member Joined: Sep 2015 From: USA Posts: 2,585 Thanks: 1430 
$I = \displaystyle \int_0^2 \int_{x}^{xx^2}~dy~dx$

July 25th, 2019, 10:18 PM  #3 
Newbie Joined: Nov 2018 From: Iran Posts: 12 Thanks: 0 Math Focus: calculus  
July 25th, 2019, 11:01 PM  #4 
Senior Member Joined: Sep 2015 From: USA Posts: 2,585 Thanks: 1430  
July 26th, 2019, 12:14 AM  #5 
Newbie Joined: Nov 2018 From: Iran Posts: 12 Thanks: 0 Math Focus: calculus  Notation like f(x,y) kind of thing. Or it's not needed?
Last edited by skipjack; August 1st, 2019 at 09:48 AM. 
July 26th, 2019, 06:40 AM  #6 
Senior Member Joined: Sep 2015 From: USA Posts: 2,585 Thanks: 1430  It's a definite integral. It's not a function of $x$ and $y$. Those just serve as dummy variables for the integral.
Last edited by skipjack; August 1st, 2019 at 09:49 AM. 
August 1st, 2019, 08:49 AM  #7 
Newbie Joined: Nov 2018 From: Iran Posts: 12 Thanks: 0 Math Focus: calculus 
So the integral is wrong? I mean, is there no way of calculating that area with double integral?
Last edited by skipjack; August 1st, 2019 at 09:47 AM. 
August 1st, 2019, 08:54 AM  #8  
Senior Member Joined: Sep 2015 From: USA Posts: 2,585 Thanks: 1430  Quote:
I just said that the integral as given is a definite number. It's not a function of x or y. Last edited by skipjack; August 1st, 2019 at 09:47 AM.  
August 1st, 2019, 09:51 AM  #9 
Global Moderator Joined: Dec 2006 Posts: 21,028 Thanks: 2259  

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