三分之一[2x-(x2+1/2x-3)]-(2x2+2)
=1/3(2x-x²-1/2x+3)-2x²-2
=-1/3x²-1/2x+1-2x²-2
=-7/3x²-1/2x-1
如果本题有什么不明白可以追问,1/2x-[2x-(x^2+ 1/2x-3)]-(2x^2+ 2)化简