原式=3³×(x²)³-7x³(x³-x×4x²-x×1)+x^4=27x^6-7x³(x³-4x³-x)+x^4=27x^6-7x³(-4x³-x)+x^4=27x^6-7x³×(-4x³)-7x³×(-x)+x^4=27x^6+28x^6+7...