the rule is: if
where are your x's coming from?
EDIT: Oh! i see now, you put red z to mean !
still, where are you getting your x's from?!
For one thing it surely does not say "write the QUESTION in the form a+bi". Perhaps it says "write the ANSWER in the form a+ bi.
But then "5(x+ 3)(x-2)^2(x+1)" is NOT in the form a+ bi!
As you said before , a positive real number, not some product of algebraic expressions. Perhaps you accidently looked up the answer to the wrong question.