Question

已知函数f（x）=2的x次方减去2的负x次方/2的x次方加2的负x次方（1）求函数的定义域和值域（2）证明

Answer 1

令2^x=t(t>0) 则2^-x=1/t f(t)=(t- 1/t)/(t+ 1/t)=(t^2-1)/(t^2+1)

=1- 2/(t^2+1) t^2+1>1 0