Hey guys I'm not sure whether my approach to this question is right...kinda looks simple enough eh?

QUESTION

One root of is . Find the other root of this equation and the value of K in the form

So this is what I did:

Since is a root, is also a root as complex roots come in conjugate pairs

But then?

have I misunderstood something?...im rusty with complex numbers

The actual answers are that the other root is ,and

Thanks