f(x)=log1/2(x^2-3x+2)
x^2-3x+2>0
解得x2
即定义域为(-∞,1)U(2,+∞)
真数t=x^2-3x+2=(x-3/2)^2-1/4
当x2时,t∈(0,+∞)
∴log(1/2)t∈R
即f(x)的值域为R