解:5-√2a=2b+2/3√2-a,则5-2b+a=√2a+2/3√2.故: 5-2b+a=(√2)×(a+2/3).等式的左边为有理数,故右侧也为有理数.∴有理数a+2/3=0, 得a=-2/3.则5-2b+a=0,5-2b-2/3=0, b=13/6.所以,a-b=-2/3-13/6= -17/6....