y = 1 / (1 - 1) = 1 / 0
This is not 0, it is undefined. In this particular equation, it is either negative or positive infinity.
You're just unlucky with the coordinates you picked to graph it.
Try x =
1/4 - 1
1/2 - 1
1 - 1
2 - 1
4 - 1
8 - 1
Do the same for the negative side.
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