One of the two things being multiplied must be zero, so either *x* – 3 = 0 or *x* + 7 = 0.

If *x* + 7 = 0, then *x* = –7. In that case, we can substitute into *x* – 3:

*x* – 3

= –7 – 3

= –10

So *x* – 3 can equal 0 or –10.

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