证明在定义域内有界 ∵(x2+1)≥1(x2+1)≤(x2+1)2f(x)|=|(x2+1)(x?+1)|≤(x2+1)2(x?+1)而(x2+1)2(x?+1)(x?+1+2x2)(x?+1)1+2x2(x?+1)≤1+(x?+1)(x?...