>>10
You can't just use linear functions to prove such a general statement. That is so basic and flawed reasoning. As
>>10 said, multiplying with zero is totally different with dividing by 0. If you learnt functions and limits, you would know that by dividing any polynomial by zero, you would get a vertical asymptote. Thus it has an infinite range which would be undefined for a particular x value(s). It has EVERYTHING to do with limits.