Question

在反比例函數(shù)y=中，當(dāng)x＞0時(shí)，y隨x的增大而減小，則二次函數(shù)y=ax²﹣ax的圖象大致是下圖中的（　　）                                              

A．            B．             C．            D．

　                                                                                                      

Answer 1

A【考點(diǎn)】二次函數(shù)的圖象；反比例函數(shù)的性質(zhì)．                                          

【專題】壓軸題；數(shù)形結(jié)合．                                                                  

【分析】根據(jù)反比例函數(shù)的性質(zhì)判斷a的符號；再根據(jù)a的符號，判斷二次函數(shù)y=ax²﹣ax的圖象大致位置．               

【解答】解：由已知，根據(jù)反比例函數(shù)的性質(zhì)可得a＞0；                              

所以拋物線y=ax²﹣ax的開口向上，應(yīng)排除C、D；                                        

因?yàn)閤=﹣=﹣＞0，所以拋物線的對稱軸在y軸的右側(cè)，排除B．                  

故選A．                                                                                            

【點(diǎn)評】根據(jù)函數(shù)中字母系數(shù)的符號來確定函數(shù)圖象的大致位置，體現(xiàn)了數(shù)形結(jié)合的思想．