Hello, Greg mentioned that the GRE does not consider negative factors. I had a question about how this fact applies to a problem Greg went over in Arithmetic and Algebra Session 7 at minute 38:17.

This question gave 2 equations: √(2x) = 4 and y^2 = 64 then asked us to compare X and Y. Greg stated that Y = +8 and -8, which I understand, but I ignored the -8 because -8 is a negative factor of 64. Therefore, I thought that X and Y were equal and chose C. How do we know that this is an exception to the overall idea that GRE doesn’t consider negative factors? Are problems using roots/exponents always exceptions? What other exceptions may we come across?

Thank you!