Regular expressions

[Rano1234]

Questions so recently ive been doing regular expressions questions, i understand the basic concept of how to write down strings of the language provided, however im slightly confused about how to approach them with the combinations shown,My attempt i attempted question (a) and am not sure if im on the right path, also if anyone could send any tutorials about this i would be grateful as i cant seem to find any. Thanks

 

[Deleted member 4993]

Questions so recently ive been doing regular expressions questions, i understand the basic concept of how to write down strings of the language provided, however im slightly confused about how to approach them with the combinations shown,My attempt i attempted question (a) and am not sure if im on the right path, also if anyone could send any tutorials about this i would be grateful as i cant seem to find any. Thanks

What is "?" in the context of 1(b) and 1(c)!

 

[Rano1234]

Well when looking at an example set by my teachers its this, pretty sure its a rule for regular expressions

 

[Deleted member 4993]

Well when looking at an example set by my teachers its this, pretty sure its a rule for regular expressions
View attachment 14641

To repeat my question - what is "?" in the context of 1(b) and 1(c)!

What does "?" do in that expression!