Regular expression in theory of computation solved examples Part – 2

Solution:

We have the input alphabets ∑ = {A, . . . ., Z, a, . . . . , z}

Here, the resultant regular expression will denote the set of all string over the given ∑ which contains occurrence of x’s three times.

In the first step, let us assume that

            <letter> = {A, . . . , Z, a, . . . . . z}

Thus, the regular expression for the set of all strings over the given ∑ can be written as-

<letter>*

Thus, the required resultant regular expression which denotes the set of all strings that contains 3 x’s over the given ∑ can be written as-

            <letter>* x <letter>* x <letter>* x <letter>*