http://i71.photobucket.com/albums/i1...4/Untitled.jpg

Can someone please explain to me the red circle? I don't understand how the previous step results in 1/infinity divided by infinity which then equals to zero..?

Also, I don't understand anything in the picture below, so can someone also explain each step to me?

http://i71.photobucket.com/albums/i1...ionz04/4-1.jpg

Thank you!