It's a mistake I made all the time, until my physics teacher taught me to ALWAYS plug the numbers in BEFORE changing the equation in any way (he took off points if you didn't, even if you came up with the right answer... but he gave 80% on tests an "A" (with no minus ), so I'm happy with him).

and, given the nature of infinity, even though anything times 0=0, infinity is kindof a special case, inft*0 doesn't neccecarely equal 0... I'm not sure how to quote this, because my father is a Math proffesser at a College here in town and he told me that, so I'm sure it's true, and maybe the maths people can explain it better than I can, but glad to be of help!

Lol yea, this thing about singularities has always bothered me. I guess my maths skills arent up to the job of understanding it without a bit of explanation. Thanks for your help