This is a question in my logic class.
- $(\exists x)(Px \land Lxa)$
- $(y)(Py \supset Lay)$
- $(x)(y)[(Lxa \land Lay) \supset Lxy]$
- $(\exists x)[Px \land (y)(Py \supset Lxy)]$
So far what occurs to me is that EI 1,
$$Pu \land Lua$$ then UI 2,
$$Pu \supset Lau$$
Through MP I can get $$Lau$$ Since I have $Lau$ and $Lua$, So I can UI 3 and get $$Luv$$ Here's where I'm stuck at. Since $u$ showes up in a EI line, I can't use UG to get $$(y)(Py\supset Lxy)$$
Any idea? By the way, is there any general tips to these questions? Thanks!