原式＝x^2(x^2+2x-1)-(1-x)(x^3-2x)
＝x^4＋2x^3－x^2－(x^3-2x)＋x(x^3-2x)
＝x^4＋2x^3－x^2－x^3＋2x＋x^4－2x^2
＝2x^4＋x^3－3x^2＋2x