y=√2x-1 -√1-2x +8x有意义
则2x-1≥0,1-2x≥0
则x≥1/2,x≤1/2
则x=1/2
代入,得y=0-0+8×1/2=4
√4x+5y-6=√(2+20-6)=√16=4