Question Discussion & Solution

Let L = L1 ? L2, where L1 and L2 are languages as defined below:
L1 = {ambmcanbn | m, n >= 0 }

L2 = {aibjck | i, j, k >= 0 }

Then L is

Consider alphabet ? = {0, 1}, the null/empty string ? and the sets of strings X0, X1 and X0.How are X1 and X2 are related ?
X0 = 1 X1

X1 = 0 X1 + 1 X2

X2 = 0 X1 + {?}

Which one of the following represents the strings in X0?