因为,a+1/a=-2所以,(a+1/a)²=a²+1/a²+2=4,即,a²+1/a²=2,则,(a-1/a)²=a²+1/a²-2=2-2=0所以,a-1/a=0a^4-1/a^4=(a²+1/a²)(a+1/a)(a-1/a)=0