Ignore tutor @MathTherapy's pronouncement of what the correct answers are. He likes to demonstrate his presumed superiority by declaring that other tutors' answers are incorrect.
In this problem, his answers are NOT correct; the response from the other tutor shows the correct answers.
If the problem stated that the given solutions were the solutions to an equation with real coefficients, then the solution x=3i would require a complementary factor of x=-3i -- and tutor @MathTherapy's response would be correct.
But the problem says nothing about the coefficients of the equation for which the solutions are given.
So, for the question as stated, the other tutor's answers are exactly correct.