f(-x)={1/[2^(-x)—1] + 1/2}(-x) ( 你题少打了括号)
={2^x/[1—2^x] + 1/2}(-x)
={[-(1-2^x)+1]/[1—2^x] + 1/2)(-x)
={-1+1/[1—2^x] + 1/2)(-x)
={1/(1-2^x)- 1/2)(-x)
={1/(2^x-1 )+1/2)x
=f(x)
又f(x)的定义域为x≠0
所以f(x) 偶函数.
f(-x)={1/[2^(-x)—1] + 1/2}(-x) ( 你题少打了括号)
={2^x/[1—2^x] + 1/2}(-x)
={[-(1-2^x)+1]/[1—2^x] + 1/2)(-x)
={-1+1/[1—2^x] + 1/2)(-x)
={1/(1-2^x)- 1/2)(-x)
={1/(2^x-1 )+1/2)x
=f(x)
又f(x)的定义域为x≠0
所以f(x) 偶函数.