Question

a+a分之1=根号7，则a-a分之1的值

Answer 1

因为a+a分之1=根号7 所以(a+1/a)^2=7 而(a+1/a)^2-4a*1/a=(a-1/a)^2 所以(a-1/a)^2 =7-4=3 所以a-a分之1=√3

Answer 2

(a+1/a)�0�5=a�0�5+1/a�0�5+2=7,所以a�0�5+1/a�0�5=5，(a-1/a)�0�5=a�0�5+1/a�0�5-2=3，所以a-1/a=根3。

Answer 3

a+1/a=√7(a+1/a)^2=7a^2+2+1/a^2=7a^2+1/a^2=5a^2-2+1/a^2=3(a-1/a)^2=3a-1/a=±√3

Answer 4

(a+1/a)^2=7a^2+(1/a^2)+2=7a^2+(1/a^2)=5a^2+(1/a^2)-2=3a-1/a=√3

Answer 5

3