Let $a,$ $b,$ $c$ be real numbers such that $a + b + c = 0.$  Find the set of all possible values of $ab + ac + bc.$
Question:
Let $a,$ $b,$ $c$ be real numbers such that $a + b + c = 0.$  Find the set of all possible values of $ab + ac + bc.$
Answer:
Let's think step by step.

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Let $a,$ $b,$ $c$ be real numbers such that $a + b + c = 0.$  Find the set of all possible values of $ab + ac + bc.$
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