|-a²-2a|=√2，（-a²-2a）²=（√2）²，（a²+2a+√2）（a²+2a-√2）=0，可知a²+2a+√2=（a²+2a+1）+（√2-1）=（a+1）²+（√2-1）＞0，所以a²+2a-√2=0，a²+2a+1=√2+1，（a+1）²=√2+1，a+1=±√（√2+1），a1=√（√2+1）-1，a2=-√（√2+1）-1
