Two roots of a 3-degree polynomial equation are 5 and - 5. Which of the following cannot be the third root of the equation?

0

-5i

-5

5i

5

- 5i and 5i

Step-by-step explanation:

The Fundamental theorem of Algebra states that a polynomial of degree 3 has 3 roots, real and / or complex.

Complex roots occur in conjugate pairs.

Given 2 real roots x = 5, x = - 5

There cannot be complex roots as they occur in pairs which would result in the polynomial having 4 roots instead of 3.