Is x2 equals y2 plus 7 a function?

Answer 1

Possibly. It is not standard to but a number after a letter (e.g X or Y), so I'm not sure if you mean

2x = 2y + 7, or

x^2 = y^2 +7 (Say, "X squared equals y squared plus 7).

Both of those are functions. But it is mathematically "bad grammar" to put the number after the letter, as it makes it unclear if you have missed off the ^ sign to indicate that it should be a power. If the question box does not let you enter a ^ symbol, write "squared", or "cubed", or whatever the power happens to be . :)