先化简再求值:x(2x+1)(2x-1)-(x-3)(x^2+3x+9),其中x=2分子1解：x(2x+1)(2x-1)-(x-3)(x^2+3x+9)=x(4x^2-1)-(x^3-3^3)=4x^3-x-x^3+27=3x^3-x+27=3×1/8-1/2+27=27-1/8=26又7/8
