Question

已知X²-3X+1=0,(X不等于0),求X四次方+1/X的四次方的值

Answer 1

两边同除x得

x-3+1/x=0

x+1/x=3

x^4+1/x^4

=(x^2+1/x^2)^2-2

=[(x+1/x)^2-2]^2-2

=47