Question

若函數(shù)的圖象的頂點(diǎn)在第四象限，則函數(shù)的圖象是（ ）．

          

 

Answer 1

【答案】

A

【解析】

試題分析：先判斷函數(shù)f（x）的單調(diào)性，根據(jù)當(dāng)導(dǎo)函數(shù)大于0時(shí)原函數(shù)單調(diào)遞增，當(dāng)導(dǎo)函數(shù)小于0時(shí)原函數(shù)單調(diào)遞減得到答案．解：函數(shù)f（x）=x²+bx+c是開(kāi)口向上的二次函數(shù)，定點(diǎn)在第四象限說(shuō)明對(duì)稱軸大于0,根據(jù)函數(shù)f（x）在對(duì)稱軸左側(cè)單調(diào)遞減，導(dǎo)函數(shù)小于0；在對(duì)稱軸右側(cè)單調(diào)遞增，導(dǎo)函數(shù)大于0知，A滿足條件,故選A

考點(diǎn)：函數(shù)的單調(diào)性

點(diǎn)評(píng)：本題主要考查函數(shù)的單調(diào)性與其導(dǎo)函數(shù)的正負(fù)之間的關(guān)系，即當(dāng)導(dǎo)函數(shù)大于0時(shí)原函數(shù)單調(diào)遞增，當(dāng)導(dǎo)函數(shù)小于0時(shí)原函數(shù)單調(diào)遞減