合并同类项,
3x^2-[7x-(4x-3)-2x^2]光求值:1/2x-2(x-1/3y^2)+(-3/2x+1/3y^2)其中x=-2,y=2/3.3y^4-4x^3y+0.2x^2y^2-4y^4+0.5x^3y-1/5x^2y^2其中x=-2,y=0.3