Question

已知代数式2x^2+ax-y+6-2bx^2+3x-5y-1的值与x的取值无关,求3分之1a^3-2b^2-4分之1a^

Answer 1

2x^2+ax-y+6-2bx^2+3x-5y-1

=(2-2b)x^2+(a+3)x=6y+5

x的取值无关

2-2b=0

b=1

a+3=0

a=-3

1/3a^3-2b^2-1/4a^3+3b^2

=1/12a^3+b^2

=1/12(-3)^3+1^2

=-9/4+1

=-5/4