EQ_{CFG} = { < G1,G2 > | G1 and G2 are CFGs and L(G1) = L(G2)}
is undecidable.
CFL_{TM} = { < M > | M is a TM and L(M) is a context free language}
is undecidable.
Prove that if A <=_{m} B then A^{C} <=_{m} B^{C}.
REV_{TM} = { < M > | M is a TM and L(M) ={ww^{R} | w belongs to Sigma*}}
is undecidable.
EI_{TM} = { < M1,M2 > | M1 and M2 are TMs and the intersection of L(M1) and L(M2) is empty}