代数式4X平方加2ax减½y加6减4bx平方减8X减5Y减3的值与X无关
=4x^2+2ax-1/2y+6-4bx^2-8x-5y-3
=(4-4b)x^2+(2a-8)x-1/2y+3-5y
4-4b=0 2a-8=0
a=4 b=1