Question

数学题~~在线等！！！！

函数y=log2[x+1/(x-1）+5](x＞1)的最小值为多少

Answer 1

y=log2[x+1/(x-1）+5]=log2[(x-1)+1/(x-1)+6]
x>1
x-1>0
(x-1)+1/(x-1)>=2且（x-1)=1/(x-1)即x=2取=号
y=log2[(x-1)+1/(x-1)+6]>=log2[2+6]=3
最小值为3

Answer 2

令x-1=t，则y=log2{t+1/t+6}>=log2[2+6]=3
最小值为3