Question

http://prntscr.com/9slyk6

Answer 1

@ganeshie8

Answer 2

@DanJS

Answer 3

if the denominator there becomes a zero at some point, then you have an undefined function,

Answer 4

notice if you move close to x=4 from either side of 4, the bottom will become very very small + from the + side, and very very small - from the - side.

there is a vertical line at x=4 that the graph can not deal with, the closer you move x to 4, the larger out of control y will become, off to infinity, and still never reaching x=4