(x+1)(x²+1)(x³+1)≥8x³证明：因为x²+1-2x=(x-1) ²≥0 故：x²+1≥2x(x+1)(x²+1)(x³+1)＝(x+1)(x²+1)(x+1)（x²+1-x）＝(x+1) ² (x²+1)（x²+1-x）...