I wondered whether I would say this, but I just can't be silent since i'm studying mathematics x)

In real number area there are no such numbers as "+inf" or "-inf", so therefore you can't divide a (let a be any real number) by "infinity"

What you are referring is, if you take function f(x)=a/x and take limit what happens, when you increase "x towards infinity" to the value of function, and you say:

a/x -> 0 when x -> oo.

Which is to be read a/x convergences towards zero, when x grows limitlessly.

And a/0 is not defined and it doesn't have a remainder..

btw if you take what happens when you have the same function f(x)=a/x and let x go towards zero from left side and you get

a/x -> oo, when x-> 0-

so when x go towards zero from left f(x) grows limitlessly.

Hope this helps.