- #1
calvino
- 108
- 0
Determine with justification which sets are open, closed, or neither
i) {(x,y,z): x^2+ y^2 + z^2 +(xyz)^2 >= -1}
ii) {(x,y,z): x^2 + y^2 +z^2 >= 1}
iii) {(x,y,z): x^2- y- z >1}
iv) {(x,y): 3>= x^2- xy + y^2 >1
v) {(x,y): x^2 - y^2 >=0 }
So, my first insinct is to go about it using the definition of open sets. So I try and find a neighbourhood around a point in the set that is not completely contained in the set. What confuses me is that that method is not very definite. What if I can't find that neighbourhood?
Any help on how I should go about starting this question off?
i) {(x,y,z): x^2+ y^2 + z^2 +(xyz)^2 >= -1}
ii) {(x,y,z): x^2 + y^2 +z^2 >= 1}
iii) {(x,y,z): x^2- y- z >1}
iv) {(x,y): 3>= x^2- xy + y^2 >1
v) {(x,y): x^2 - y^2 >=0 }
So, my first insinct is to go about it using the definition of open sets. So I try and find a neighbourhood around a point in the set that is not completely contained in the set. What confuses me is that that method is not very definite. What if I can't find that neighbourhood?
Any help on how I should go about starting this question off?