Question

a的平方减a减1等于0 那a的4次方加a的四次方分之一等于多少

Answer 1

a^2-a-1=0

a^2-1=a

a-1/a=1

(a-1/a)^2=1

a^2-2+1/a^2=1

a^2+1/a^2=3

(a^2+1/a^2)^2=9

a^4+2+1/a^4=9

a^4+1/a^4=7