Write the polynomial in standard form and identify the x-intercept, as well as the zeros for
f(x) = (x - 3i)(x - 3i)

Well, ok, the x intercepts aer where the function equals 0
also
if the x intercepts are r1 and r2 then the factored form of the function is
f(x)=a(x-r1)(x-r2) where a is a constant
well, we have it already in that form

f(x)=(x-3i)(x-3i)
the x intercept is at x=3i
standard form requires expansion
we expand to get
f(x)=x²-6i-9

Looks pretty good to me!