∴2xy=x2+y2﹣(x﹣y)2=17﹣9=8,
∴(x+y)2=x2+y2+2xy=17+8=25,
∴x+y=5,xy=4,
∴原式= 同类题1 下列四组函数中,表示相等函数的一组是( )
This is my room (房间).I have a new desk and a chair.The book is on the desk.The ruler is under the book.My eraser is in the pencil box.My bag is on the chair.Where's my cat? It's under the chair.It's sleeping (睡觉).