If we have one zero of +5i, we also have to have its conjugate which is -5i. Therefore, the factors that we will FOIL to get that polynomial are (x+5i)(x-5i). That distribution results in [tex] x^{2} -25 i^{2} [/tex]. I'm sure by now you know that i squared is equal to -1, so -25(-1) = 25. So our polynomial is [tex] x^{2} +25=y[/tex]
