函數(shù)Y=f(x)是定義在0,+∞上的減函數(shù)滿足f(xy)=f(x)+f(y),f(1/3)=1 求f(x)+f(2-x)
函數(shù)Y=f(x)是定義在0,+∞上的減函數(shù)滿足f(xy)=f(x)+f(y),f(1/3)=1 求f(x)+f(2-x)<2 時(shí)x的取值范圍
優(yōu)質(zhì)解答
f(xy)=f(x)+f(y)
所以,f(1/9)=f(1/3)+f(1/3)=2
f(x)+f(2-x)<2
即f[x(2-x)]減函數(shù)得:x(2-x)>1/9
2x-x^2>1/9
x^2-2x+1/9<0
(x-1)^2<8/9
1-2根號(hào)2/3定義域:x>0,2-x>0,即0綜上所述,解是1-2根號(hào)2/3