Functional Dependency Term [closed]

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I'm trying to figure out some issues about functional dependencies (databases). Is this implication true or false and why?

if A->B then AC->B

Thank you so much!

My solution:

Assume that A is a subset of B then B->A (Armstrong rule). Therefore AC->B because A is a subset of AC. If AC->A and A->B then AC-> B, according to transitivity rule.

Answer 1

If A alone functionally determines B then adding redundant attributes to the left hand side of the relationship will not alter the truth of the original dependency.

Basically this is the Augmentation rule form Armstrons Axioms which states that if A -> B then A,C -> B,C. Then by decomposition A,C -> B