문제의 7번째 조건에서

Negated terms should apear as a subtracted unnegated term (with the exception of a negative leading term which should appear as described above.) That is, rather than x^2 + -3x, the output should be x^2 = 3x.

라고 되어있는데

Negated terms should apear as a subtracted unnegated term (with the exception of a negative leading term which should appear as described above.) That is, rather than x^2 + -3x, the output should be x^2 - 3x.

이렇게 바뀌어야 하지 않나 싶어서 문의 드립니다.