Question

a的平方减a减1等于0怎么算

Answer 1

答案如下：
∵a²-a-1=0 ∴a²=a+1 ∴a²+1/a²=(a+1)+1/(a+1) =(a²+2a+2)/(a+1) =(a+1+2a+2)/(a+1) =3