NP-hard or not: partition with irrational input or parameter
The problem you have stated probably contains an error:


  Given a set $N$ with $n+2$ numbers,​ such that the first $n$ numbers are positive and rational with sum $1$, the $(n+1)$st number is $\sqrt{2}$, and the $(n+2)$nd number is $2 - \sqrt{2}$, determine whether there is a subset of $N$ such that the sum of the subset is $3/2$.


The answer is that there is never any such subset. Either the subset includes $\sqrt{2}$ and $2 - \sqrt{2}$, or neither. If it includes neither, then the sum is less than or equal to $1$. If it includes both, then the sum is greater than or equal to $2$. So the sum of the subset will never be $3/2$.