Question 1074491
{{{a(x-3)(x-4i)(x+4i)=F(x)}}}


{{{F(x)=a(x-3)(x^2-16i^2)}}}


{{{F(x)=a(x-3)(x^2+16)}}}


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{{{-40=a(2-3)(4+16)}}}


{{{-a*20=-40}}}

{{{a=2}}}


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{{{highlight(F(x)=2(x-3)(x^2+16))}}}
You can fully multiply the right hand side and put in general form if you want.