Two nonzero real numbers $a$ and $b$ satisfy $ab = a - b.$ Find all possible values of $\frac {a}{b} + \frac {b}{a} - ab.$

Enter all possible values, separated by commas.
Question:
Two nonzero real numbers $a$ and $b$ satisfy $ab = a - b.$ Find all possible values of $\frac {a}{b} + \frac {b}{a} - ab.$

Enter all possible values, separated by commas.
Answer:
Let's think step by step.

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2
Two nonzero real numbers $a$ and $b$ satisfy $ab = a - b.$ Find all possible values of $\frac {a}{b} + \frac {b}{a} - ab.$

Enter all possible values, separated by commas.
train