Can you prove that the fraction field Q of an integral domain A is the smallest field that contains A?
I.e. Assume that K is a field such that
Start by showing this...
Edit: I might have take [itex]\subseteq[/itex] a bit too liberal in the last equation. Formally, there only exists an injective ring morfism [itex]Q\rightarrow K[/itex]. But I see that as the same thing as a subset...