第1个回答 2011-01-20
x^2-3x+1=0
(x-3/2)^2=5/4
x1=3/2+√5/2
x2=3/2-√5/2
x^2+1/x^2
=(3/2+√5/2)+1/(3/2+√5/2)^2
=(3/2+√5/2)+(3/2-√5/2)^2/(9/4-5/4)^2
=(3/2+√5/2)+(3/2-√5/2)^2
=9/4+5/4+3√5/2+9/4+5/4-3√5/2
=7
x^2+1/x^2
=(3/2-√5/2)+1/(3/2-√5/2)^2
=(3/2-√5/2)+(3/2+√5/2)^2/(9/4-5/4)^2
=(3/2-√5/2)+(3/2+√5/2)^2
=9/4+5/4-3√5/2+9/4+5/4+3√5/2
=7