why is the infinite intersection of regular languages not regular ?

Question

I have gone through this link but still couldn't understand this , it is telling according to demorgan's law ,Now If I consider L to be an irregular language so 

(L1'∪L2'∪L3'∪......infinite)'= Now this will give infinite intersection of regular languages ,and this is irregular ,but how ?

http://www.eecs.berkeley.edu/~luca/cs172-07/solutions/practice1-sol.pdf

Answer 1

let we have regular languages like {a,b}, {a^2,b^2},{a^3,b^3}.......

now we will do infinite union of all these regular languages and we get {a^n,b^n | n>=1} which is a well know DCFL but not regular

Comments

Question is asking about intersection.