已知函数f(x)=(x-1⼀x+1)^2(x>1).

2025-01-08 07:43:01
推荐回答(4个)
回答1:

已知函数f(x)=[(x-1)/(x+1)]²,(x>1);若不等式(1-√x)fֿ¹(x)>a(a-√x)对一切x∈[1/4,1/2]恒成立,求
a的取值范围
解:y=[(x-1)/(x+1)]²,定义域:x>1;值域0y(x+1)²=(x-1)²;yx²+2yx+y=x²-2x+1;(y-1)x²+2(y+1)x+y-1=0;
∵x>1,∴x={-2(y+1)-√[4(y+1)²-4(y-1)²]}/[2(y-1)]=[-2(y+1)-4√y]/[2(y-1)]=-(y+2√y+1)/(y-1)
=-(√y+1)²/(√y+1)(√y-1)=-(√y+1)/(√y-1)=(1+√y)/(1-√y) (0[说明:若根号前取+号,则不能保证x>1]
故fֿ¹(x)=(1+√x)/(1-√x),(01+√x>a(a-√x)对一切x∈[1/4,1/2]恒成立;
即有a²-1-(a+1)√x<0对一切x∈[1/4,1/2]恒成立;
(a+1)(a-1)-(a+1)√x=(a+1)(a-1-√x)<0
故得-1即-1

回答2:

看不懂啊

回答3:

你先把题目写清楚吧

回答4:

用公式编辑器写清楚吧