Context free grammar examples solved

Language = {an b an+3 | n >=0}

CFG 

S-> a S a | a X a

X -> bC

C -> aaa

Valid strings

These strings must be accepted by our Context-free Grammar.

{ abaaaa, aabaaaaa, aaabaaaaaa,……… }

InValid strings

These strings must be rejected by our Context-free Grammar.

{ aba, aabaa, abba,……… }