If the two solutions to the equation are the same you only need to enter one
Merge pull request #46318 from petercollingridge/extra-sol2

If the two solutions to the equation are equal you only need to enter it once.
Fix #46282, #46279

Test plan: try the ignore-extraneous exercise type, ideally waiting for the 1 in 21 chance that the two solutions are equal.

Auditors: eater, alpert