I need to say Is language $a^mb^nc^n, m \not= n$ context free
I managed to find a grammar for $L1 = $ { $a^lb^mc^n | l=m$ or $m = n$ }, but I couldn't find the one I needed. Maybe it is impossible, but than why? If it may be helpful, that is the grammar for L1 wich i found: $A \rightarrow \epsilon |aAb, B \rightarrow \epsilon|bBc, S1 \rightarrow A|S1c, S2 \rightarrow B|aS2, S\rightarrow S1|S2$
I think that is not context free at all but I don't know how to proof.