Question

若x²-x-1=0，則=

1. A.
   0
2. B.
   
3. C.
   
4. D.
   

Answer 1

C
分析：先由x²-x-1=0，得出x²-x=1，再將改寫成x²（x²-x）-x（x²-x）+（x²-x）+，然后把x²-x=1代入即可．
解答：∵x²-x-1=0，∴x²-x=1．
∴=x²（x²-x）-x（x²-x）+（x²-x）+
=x²-x+1+
=1+1+
=2+．
故選C．
點評：本題考查了代數(shù)式求值，運用整體代入思想將x²-x=1代入變形后的式子是解題的關(guān)鍵，將式子變形為x²（x²-x）-x（x²-x）+（x²-x）+是難點．