2（x+1）²-4（x+1）（x-1）+3(x-1)².=2(x²＋2x＋1)-4(x²-1)+3（x²-2x＋1）=2x²＋4x＋2-4x²＋4+3x²-6x＋3=x²-2x＋9
2(x+1)^2-4(x+1)(x-1)+3(x-1)^2=2(x+1)[(x+1)-2(x-1)]+3(x-1)^2=2(x+1)(3-x)+3x^2-6x+3=-2x^2+4x+6+3x^2-6x+3=x^2-2x+9
