method?

This is taught in high school - or at least it was for me back in the day.

See http://www.bced.gov.bc.ca/irp/pdfs/mathematics/WNCPmath1012/2008math_precalc12.pdf Learning goal B10 goal 10.1

So I'd expect they have seen this before.

Since solution 2 doesn't rely on this trick as heavily any more, I think it's okay as is now.