题目

用配方法解方程x2﹣2x﹣2=0，下列配方正确的是（　　）                              A．（x﹣1）2=2           B．（x﹣1）2=3           C．（x﹣2）2=3           D．（x﹣2）2=6 答案：B【考点】解一元二次方程-配方法．                                                        【分析】根据配方法的一般步骤：（1）把常数项移到等号的右边；（2）把二次项的系数化为1；（3）等式两边同时加上一次项系数一半的平方得出即可．                                                            【解答】解：∵x2﹣2x﹣2=0，                                                                 ∴x2﹣2x=2，                                                                                      ∴x2﹣2x+1=2+1，                                                                              ∴（x﹣1）2=3．                                                                                 故选：B．                                                                                           【点评】此题考查了配方法解一元二次方程，解题时要注意解题步骤的准确应用．选择用配方法解一元二次方程时，最好使方程的二次项的系数为1，一次项的系数是2的倍数．                                   　                                                                                                       3．已知实数a，b分别满足a2﹣6a+4=0，b2﹣6b+4=0，且a≠b，则a2+b2的值为（　　）                 

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