解方程：x2-2x=2．
方程的两边同时加1得，x2-2x+1=2+1，
即（x-1）2=3，
故x-1=±3，
x1=1+3，x2=1-3．
To their great ___, they got the bad news that their English teacher had been in hospital for quite a few days.
A．joy
B．disappointment
C．happiness
D．sadness
关于更换变压器的回收年限，一般考虑当计算的回收年限小于5年时，变压器（）更新为宜。
A.应
B.应立即
C.不应
D.不可
