∃a∈R,∀n∈N\exists a \in \mathbb R, \forall n \in \mathbb N∃a∈R,∀n∈N, 有 ∣xn+1−a∣≤q∣xn−a∣(0<q<1)|x_{n+1} - a| \leq q|x_n - a| (0<q<1)∣xn+1−a∣≤q∣xn−a∣(0<q<1) ⟹ limn→∞xn=a\implies \lim_{n \to \infty} x_n = a⟹limn→∞xn=a
