函数ƒ(x)=log(1/2)(x2-2x+5)的值域是____.

函数ƒ(x)=log(1/2)(x2-2x+5)的值域是____.
【正确答案】:(-∞,-2]。解析:x2-2x+5=(x-1)2+4≥4,而0﹤1/2﹤1,log1/2(x2-2x+5)≤log1/24=-2.