Question

已知(a^2-1)/a=5,求(a^4+a^2+1)/a^2的值

Answer 1

(a^2-1)/a=5 a-1/a=5

(a^4+a^2+1)/a^2=(a^2+1+1/a^2)=(a^2-2+1/a^2)+3

=(a-1/a)^2+3=5^2+3=28

应是28,不是24