- #1
Cyn
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Homework Statement
I have a set I = {x from R3 : x1<1 v x1>3 v x2<0 x x3>-1}
Homework Equations
Open disc
B (x,r)
(sqrt (x-x0)^2 + (y-y0)^2) < r
The Attempt at a Solution
I have done, for example by x1<1, that let r = 1-x1
Then sqrt ((x-x1)^2 + (y-y1)^2) < sqrt (x-x1)^2) < r = 1-x1
So |x-x1| < 1-x1
x1-1<x-x1<1-x1
2x1 -1 < x < 1
So x<1 satisfy the inequality, so it is open. Is this correct?