So I had a task "Formulate a statement d=GCD(a,b,c) using quantifiers" on my exam which was marked as wrong - however, I don't know why is that wrong so could anybody please help me understand? I formulated it as:
$\exists_{d}\forall_{k}(((k|a)\land(k|b)\land(k|c))\Rightarrow d\geq k)$
I had the first term ($\exists_{d}$) marked as wrong. Why is that so?