Back off, buddy! He backed off on us in the last minute. & You can say something like that but you have nothing to back it UP. why "up" and not "off" here?
I love the examples supplied in the book as they are given with the foreign student in mind and they are used so simply. I love it when I see at the end of all that explanation a phrase saying "SIMILAR TO: "and it gives me the equivalent in other comparable phrasal verbs.
eBook Longman Phrasal Verbs Dictionary