languages over $\backslash$Sigma $=\{$a$,$ b$\},$ provide a context$-$free grammar for that language.

$1.$ The set of strings of the form ua where u is a palindrome.

$2.$ The set of strings that contain a length $6$ palindrome as a substring.

$3.$ The set of strings of the form a$^$i$*$b$*$a$^$j$*$b$*$a$^$k where j $=2$i $+3$k $+1($i$,$ j$,$ k in Z$0+)$

$4.$ The set of strings whose length is a multiple of $3,$ and do not contain an a

in the final third.

$5.$ The set of palindromes that do not contain baa as a substring.