How to substitute a complex number in a complex function? I know for the regular cases, but what I am after is something like this:
$\lim\limits_{z \to 1+5i} ix+y$
is it: i(1) + (5i) = 6i, or: i(1) + 5 = 5+i
?!

We usually define $z=x+yi$ so $x,\,y\in\Bbb R$, making the answer $5+i$.
