Question

下列結(jié)論正確的是

1. A.
   冪函數(shù)的圖象一定過(guò)原點(diǎn)
2. B.
   當(dāng)α＜0時(shí)，冪函數(shù)y＝x^α是減函數(shù)
3. C.
   當(dāng)α＞1時(shí)，冪函數(shù)y＝x^α是增函數(shù)
4. D.
   函數(shù)y＝x²既是二次函數(shù)，也是冪函數(shù)

Answer 1

D
對(duì)于A，只有冪指數(shù)α＞0時(shí)，冪函數(shù)的圖象過(guò)原點(diǎn)；對(duì)于B，當(dāng)α＜0時(shí)，冪函數(shù)y＝x^α在第一象限是減函數(shù)；對(duì)于C，當(dāng)α＞1時(shí)，冪函數(shù)y＝x^α在第一象限是增函數(shù)，而不能說(shuō)整個(gè)函數(shù)是增函數(shù)；對(duì)于D，顯然是對(duì)的．