# How to write a Regular Expression

I have seen that the regular expression for the set of strings beginning with a and ending with b is written as a(a+b)*b

Can some one tell me how to write this

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I’m not sure what you mean. $a(a+b)^*b$ is indeed a regular expression describing the set of strings over the alphabet $\{a,b\}$ that begin with $a$ and end with $b$. What is it that you want to write? –  Brian M. Scott Nov 25 '13 at 17:13
I want to know how it is written –  techno Nov 25 '13 at 17:15
How what is written? The regular expression is written $a(a+b)^*b$. –  Brian M. Scott Nov 25 '13 at 17:17