Since Z is Integer, then 6Z=3(2Z) and 8Z=4(2Z)
So the set of all elements in both sets 6Z and 8Z is the set of even. 2Z numbers.
2.Tk={z:|z-√2|<k}
-k<z-√2<k
√2-k<z<k+√2
Tk=(√2-k, √2+k), k=1,2,.. sequence of intervals
(√2-1, √2+1), (√2-2, √2+2), ..
Tk is

Andrew M.
03/07/18