Answer:
Option 2 and 5.
Step-by-step explanation:
It is given that two roots of a 3-degree polynomial equation are 5 and -5.
The number of roots is equal to the degree of the polynomial.
Degree of the polynomial is 3 it means the number of roots is 3.
According to the complex conjugate root theorem if a complex number a+ib is a root of polynomial P(x) then its conjugate a-ib is also the root of P(x). It means the number of complex root is always even.
Two given roots are real, so the remaining single root must be a real number.
So, 5i and -5i can not be the third root of the equation.
Therefore, the correct options are 2 and 5.
