# Confused about question on iterative method for numerical analysis

This question from my textbook on using the iterative method to find roots of an equation has confused me. I answered the question correctly but part c is the source of my confusion. I know that the answer is that the attempt will fail because you will need to take the square root of a negative number. This is the correct answer in the back of the book.

What has confused me is, where the did minus sign go in the iterative formula for part c? I had thought that whether you are finding a negative or positive root, you use the same formula, yet for the positive root they have omitted the minus sign. Why is that?

I have highlighted the relevant areas green.

Thanks very much!

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