已知a2+ab=5,ab+b2=﹣2,a+b=7,那么a﹣b=____ .
将左右两部分搭配,使其成为通顺的句子。
①Is she in the study?____ A. It's on the desk.
②Is this your bedroom?____ B. No, they aren't.
③Where's my pen?____ C. No, it isn't.
④Are they on the chair?____ D. Yes, she is.
⑤Where are my books?____ E. They are on the bed.