If AB->C is an FD for a database then does that imply A->C
I came to know that ab → c does NOT imply a → c and b → c


Correct. It does not imply either.


  ....
  So, that means that if A -> C, then we can imply AB -> C. 


Yes, correct. but the following:


  Assuming ... Is this mathematical approach not correct or I am wrong in a different way?


No, A -&gt; C is deducted from A -&gt; BC, not from AB -&gt; C.

A -&gt; BC is just a shorthand notation for A -&gt; B and A -&gt; C