Evaluating Multivariable Limit: (x^2+y^2)/(1+y^2)

marquitos
Messages
9
Reaction score
0
Multivariable Limits!

Lim (x^2+y^2)/(1+y^2)
(x,y)--> (0,0)

evaluate the limit or determine that it does not exist.
Im pretty sure that the limit does not exist because if i take it from the y and x axises the values don't match up but not really sure if that is the right way to do it. Any help would be great thank you very much.
 
Physics news on Phys.org


i apologize i think may be a very stupid question since simple substitution should most likely work but if it doesn't please inform me what i am doing wrong! Thank you again.
 


marquitos said:
i apologize i think may be a very stupid question since simple substitution should most likely work but if it doesn't please inform me what i am doing wrong! Thank you again.

The denominator approaches 1, doesn't it? I'm pretty sure the limit does exist.
 


Its a theorem that if f, g are continuous and g(x) != 0 then f/g is continuous at x. (1 + y^2) and (x^2 + y^2) are both continuous and (1+y^2) is never zero. Hence (x^2 + y^2)/(1+y^2) is continuous everywhere. So the limit is the value of the function at all points including zero.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
Back
Top