考點(diǎn):函數(shù)的圖象
專題:函數(shù)的性質(zhì)及應(yīng)用
分析:根據(jù)二次函數(shù)的對(duì)稱軸首先排除BD,再結(jié)合二次函數(shù)和指數(shù)函數(shù)的性質(zhì)逐個(gè)檢驗(yàn)即可得出答案.
解答:
解:根據(jù)指數(shù)函數(shù)y=(
)
x可知a,b同號(hào)且不相等,則二次函數(shù)y=ax
2+bx+c的對(duì)稱軸-
<0,對(duì)稱軸在y軸的左側(cè),排除B,D
因?yàn)?個(gè)選項(xiàng)中指數(shù)函數(shù)均為減函數(shù),故
<1,
當(dāng)ab同時(shí)為負(fù)數(shù),則a<b<0,二次函數(shù)的開(kāi)口向下,對(duì)稱軸
-<-
<0,
當(dāng)ab同時(shí)為正數(shù),則0<b<a,二次函數(shù)的開(kāi)口向上,對(duì)稱軸
-<-
<0,
故排除C
故選:A.
點(diǎn)評(píng):本題考查了同一坐標(biāo)系中指數(shù)函數(shù)圖象與二次函數(shù)圖象的關(guān)系,根據(jù)指數(shù)函數(shù)圖象確定出a、b的正負(fù)情況是求解的關(guān)鍵