(2x^2+ax-1/3y+1/5)-(x-2y+1-bx的平方)
=2x²+ax-1/3y+1/5-x+2y-1+bx²
=(2+b)x²+(a-1)x-1/3y+1/5+2y-1
∴2+b=0 a-1=0
∴a=1
b=-2