Question

求解求解。。求函数f(x)=x+2√x(x∈[0,4])的最大值和最小值。

Answer 1

换元法，设根号下x为t，则函数为f（x）=t*t+2t再然后二次函数的最大值最小值就会了吧=_=

Answer 2

因为f(x)=(x-1)/(x^2+1)所以1/f(x)=(x^2+1)/(x-1)=(x-1)²+2(x-1)+2/(x-1)=(x-1)+[2/(x-1)]+2当x属于[0,4]，1/f(x)∈[-2√2-2,-1]∪[2√2+2,5]所以f(x)在x∈[0,4]值域为[-5,-2√2-2]∪[1,2√2+2]