1．已知函数f(x)=ax-b/x-2ln x,f(l)=0. (1)若函数f(x)在其定义域为单调函数,求a的取值范围; (2)若函数f(x)的图象在x=1处的切线的斜率为0,且an+1= f’(1/an-n+1)-n2+1,已知a1=4,求证:an≥2n+2; (3)在(2)的条件下,试比较1/1+a1+1/1+a2+1/1+a3+…+1/1+an与1/5的大小, 并说明你的理由． 2．设f1(x)=2/1+x,定义fn+1(x)=f1[fn(x)],an=fn(0)-1/fn(0)+2,基中n∈N． 1. Known function f (x) = ax-b / x-2ln x, f (l) = 0. (1) If the function f (x) is a monotonic function in its domain, seeking a range of values; (2 ) If the slope of the tangent to the image of function f(x) at x=1 is 0, and an+1=f’(1/an-n+1)-n2+1, known a1=4, verify :an≥2n+2; (3) Under the condition of (2), compare 1/1+a1+1/1+a2+1/1+a3+...+1/1+an and 1/5. , and explain your reasons. 2. Let f1(x)=2/1+x, define fn+1(x)=f1[fn(x)], an=fn(0)-1/fn(0)+2, n基N in the base.