预            1. 将y=ax2+bx+c化为y=a(x-h)2+k的形式：                                                                                                                                                                                                                                                                                                                                                                                                                                                                  已学过的知识还有什么困惑？

             （1）你还记得完全平方公式吗？                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

习             填空：x2-4x+=（x- ）2   x2+3x+=（x+ ）2