lim(n→∞) (an² + bn - 1)/(2 - 3n² + 1) = 1lim(n→∞) (a + b/n - 1/n)/(2/n - 3 + 1/n²) = 1,上下都除以n²(a + 0 - 0)/(0 - 3 + 0) = 1a/(- 3) = 1a = - 3