原多项式为：(2x^2-2x+3)-(x^2+6x-6)=2x^2-2x+3-x^2-6x+6=x^2-8x+9正确结果是：x^2-8x+9-(x^2+6x-6)=x^2-8x+9-x^2-6x+6=-14x+15
