Question

Please help! Is -9i right?

Answer 1

If a + bi is a root of a function, then a - bi is also a root of the function.
 When we have 9i, that makes a = 0 and b = 9 
If 9i is a root of f(x) then 0 - 9i, or -9i is also a root of f(x)  -9i is correct!

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