y=（x^2+8）/（x-1）=(x-1)^2+2x+7/x-1=(x-1)^2+2(x-1)+9/x-1=x-1+ 2+ 9/x-1当x＞1时用基本不等式得y≥2根号下9 +2=8当x＜1时-(x-1)+9/-(x-1)-2≥4∴x-1+ 2+ 9/x-1小于等于-4∴y值域为[8,+无穷）∪（-无穷,-4]...