Work Step by Step
We need to write down the polynomial $f(x)$ in factored form. $f(x)=(x+1)(x-2)(x-3i)(x+3i)$ $=(x^2+x-2x-2)(x^2+9)$ $=x^4+9x^2-x^3-9x-2x^2-18$ $=x^4-x^3+7x^2-9x-18$
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