代数式（2x^2+ax-y+6)-(2bx^2-2x+5y-1)的值与字母x的取值无关（2x^2+ax-y+6)-(2bx^2-2x+5y-1)=2x^2+ax-y+6-2bx^2+2x-5y+1=(2-2b)x^2+(a+2)x-6y+72-2b=0 a+2=0a=-2 b=1代数式1/2a^2-2b^2+4ab=1/2*(-2)^2-2*1^2+4*(-2)...