Question

（07年福建卷）已知對(duì)任意實(shí)數(shù)x,有f（-x）=-f (x)，g(-x)=g(x),且x>0時(shí)f’(x)>0,g’ (x) >0,則x<0時(shí)

A.f’(x)>0,g’(x)>0                                             B.f ’(x)>0,g’(x)<0

C.f ’(x)<0,g’(x)<0                                            D.f ’(x)<0,g’(x)<0

Answer 1

答案：B

解析：由已知f(x)為奇函數(shù),圖像關(guān)于原點(diǎn)對(duì)稱,在對(duì)稱區(qū)間的單調(diào)性相同;g(x)為偶函數(shù),在對(duì)稱區(qū)間的單調(diào)性相反, x>0時(shí)f’’(x)>0,g’ (x) >0,遞增,當(dāng)x<0時(shí), f(x) 遞增, f ’(x)>0; g(x)遞減, g’(x)<0,選B