1.y=(2-sinx)/(2-cosx)的值域是_____.2.若函数f(x)=loga(x + a/x - 4)(a>0且a≠1)的值域为R,则实数a的取值范围为______.3.y=x^2/(x-3) (1≤x≤2)的值域是______.打错了,是填空题!要过程!公布答案:1.[(4-√7)/3,(4+√7)/3]2.(0,1)∪(1,4]3.[-4,-1/2]