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+7
2-2b=0 a+2=0
a=-2 b=1
代数式1/2a^2-2b^2+4ab
=1/2*(-2)^2-2*1^2+4*(-2)*1
=2-2-8
=-8
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+7
2-2b=0 a+2=0
a=-2 b=1
代数式1/2a^2-2b^2+4ab
=1/2*(-2)^2-2*1^2+4*(-2)*1
=2-2-8
=-8