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若x2-13x+1=0,則x2+1/x2=       {推甄}

(A)167

(B)169

(C)171

(D)173

       

                                                                      ANS:(A)

 

                                                                                   (x+1/x)2=x2+2+1/x2

                                                                                           132=x2+1/x2+2

                                                                                     x2+1/x2=196-2

                                                                                     x2+1/x2=167

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