Question

已知lga，lgb是方程2x－4x＋1 = 0的两个根，则(lg)的值是(  )．

(A)．4               (B)．3                 (C)．2                     (D)．1

 

Answer 1

【答案】

C

【解析】由已知lga＋lgb = 2，lga·lgb =，又(lg)= (lga－lgb)= (lga＋lgb)－4lga·lgb = 2，故选(C)．