Question

Determine if the equation x - yA = 1 defines y as a function of x.

No. At least one input results in more than one output.
Yes. One input results in one output.
No. At least one output results in more than one input.
Yes. One output results in one input.

Answer 1

Yes. One input results in one output.

Explanation:

If "A" is not dependent upon x or y, this is a linear equation. Any linear equation in two (or more) variables defines a function.

Yes, this equation defines a function.

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A function has one output for each input. The appropriate description is the one shown as the Answer.