Idon't understand how the highest common factor for −8y and 40 is 8 and the hcf for −5y and −25 is -5 and not 5. can someone explain to me?

Which questions would most a reader identify the author's purpose for writing? check all that apply. what type of text is this? what type of reviews did the book receive? how many copies of the book have been sold? what is the central idea? how does this text make one feel?