Chapter 3 - Section 3.5 - Complex Zeros and the Fundamental Theorem of Algebra - 3.5 Exercises - Page 293: 19

Zeros: +/- $5i$ Multiplicity: 2

Subtract 25 to the other side, take the square root of it, but because there is a negative under the radical, $i$ will be used. Your answer will be +/- $5i$, with a multiplicity of two because of the exponent of two.