y=-x+2√(x-1)+2令t=√(x-1),则t≤0,x=t^2+1.y=-t^2+2t+1=-(t-1)^2+2≤1,值域(-∞,1]为什么不是y=-t^2+2t+1=-(t-1)^2+2≤2值域(-∞,2]=-x+2√(x-1)+2令t=√(x-1),则t≥0,x=t^2+1.y=-t^2+2t+1=-(t-1)^2+2≤1,值域(-∞,1]为什么不

　　y=-x+2√(x-1)+2令t=√(x-1),则t≤0,x=t^2+1.y=-t^2+2t+1=-(t-1)^2+2≤1,值域(-∞,1]为什么不是y=-t^2+2t+1=-(t-1)^2+2≤2值域(-∞,2]

　　=-x+2√(x-1)+2令t=√(x-1),则t≥0,x=t^2+1.y=-t^2+2t+1=-(t-1)^2+2≤1,值域(-∞,1]为什么不是y=-t^2+2t+1=-(t-1)^2+2≤2值域(-∞,2]