—Hello! May I speak to Alice?—Sorry, she _____ Shanghai.
A：have gone to
B：has been to
C：has been in
D：has gone to
—Hi，Tony，can I use your computer for a while this afternoon?
—Sorry.________.
②方程x+ 2x =m+ 2m 的解为：x1=m；x2= 2m
③方程x- 3x =m- 3m 的解为：x1=m；x2= - 3m
归纳：④方程 x+ cx =b+ cb 的解为：x1= b ；x2= cb
应用：⑤利用④中的结论，直接解关于x的方程:x+ 2x−1 =a+ 2a−1
关山难越，____? ____，尽是他乡之客。
