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.